k&r : excercise solutions to chapter 3
Tibor Bizjak
parent
abccef71d3
commit
2d2e6880a2
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@ -0,0 +1,69 @@
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#include <stdio.h>
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#define SIZE 1000000
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#define X 2*((SIZE-1) / 2) + 1
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#define T 10000000
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int binsearch(int x, int v[], int n);
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int binsearch_old(int x, int v[], int n);
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/* run binsearch on array of size SIZE
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* if arg is provided use old binsearch */
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int main(int argc, char *argv[])
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{
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long i;
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int arr[SIZE];
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for (i = 0; i < SIZE; ++i)
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arr[i] = 2 * i;
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if (argc == 1) {
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for (i = 0; i < T; ++i)
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binsearch(X, arr, SIZE);
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printf("binsearch : %d\n", binsearch(X, arr, SIZE));
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}
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else {
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for (i = 0; i < T; ++i)
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binsearch_old(X, arr, SIZE);
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printf("old binsearch : %d\n", binsearch_old(X, arr, SIZE));
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}
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return 0;
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}
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/* binsearch: find x in sorted v of length n, using one comparison in loop */
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int binsearch(int x, int v[], int n)
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{
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int low, high, mid;
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low = 0;
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high = n - 1;
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while (low < high) {
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mid = (low + high) / 2;
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if (x <= v[mid])
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high = mid;
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else
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low = mid + 1;
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}
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if (v[low] == x)
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return low;
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return -1;
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}
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/* binsearch: find x in sorted v of length n, using two comparisons in loop */
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int binsearch_old(int x, int v[], int n)
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{
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int low, high, mid;
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low = 0;
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high = n - 1;
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while (low <= high) {
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mid = (low + high) / 2;
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if (x < v[mid])
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high = mid - 1;
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else if (x > v[mid])
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low = mid + 1;
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else
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return mid;
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}
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return -1;
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}
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@ -0,0 +1,64 @@
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#include <stdio.h>
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#include <string.h>
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#define ESCAPE_SEQS \
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X('\a', 'a') X('\b', 'b') X('\f', 'f') X('\n', 'n') \
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X('\r', 'r') X('\t', 't') X('\v', 'v')
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#define SIZE 1000
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void escape(char *s, char *t);
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void unescape(char *s, char *t);
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/* runs escape and unescape on stdin, prints results*/
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int main()
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{
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int i, c;
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char s[SIZE+1], t[2*SIZE+1];
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for (i = 0; (c = getchar()) != EOF; i++) {
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if (i >= SIZE) {
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printf("warning : buffer overflow\n");
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break;
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}
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s[i] = c;
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}
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s[i] = '\0';
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escape(s, t);
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printf("--- escaped ---\n%s\n", t);
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unescape(t, s);
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printf("\n-- unescaped --\n%s", s);
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return 0;
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}
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/* escape: makes escape sequences visible as it copies s to t
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* size of t must be 2*size of s */
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void escape(char *s, char *t)
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{
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for (; *s != '\0'; s++, t++)
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switch (*s) {
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#define X(e, c) case e : *(t++) = '\\'; *t = c; break;
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ESCAPE_SEQS
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#undef X
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default : *t = *s; break;
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}
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*t = '\0';
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}
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/* unescape: inverse of escape */
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void unescape(char *s, char *t)
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{
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for (; *s != '\0'; s++, t++) {
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if (*s == '\\')
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switch (*(s+1)) {
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#define X(e, c) case c : *t = e; s++; continue;
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ESCAPE_SEQS
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#undef X
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}
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*t = *s;
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}
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*t = '\0';
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}
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#include <stdio.h>
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#include <ctype.h>
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#define SIZE 1000
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/* check if c1-c2 is valid range */
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#define IS_RANGE(c1, c2) ( \
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(isdigit(c1) && isdigit(c2)) || \
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(islower(c1) && islower(c2)) || \
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(isupper(c1) && isupper(c2)) \
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)
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int getstr(char *s, int n);
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void expand(char *s, char *t, int n);
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/* copy stdin to string, run expand, print output */
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int main()
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{
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char s[SIZE], t[SIZE];
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if (getstr(s, SIZE) < 0)
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printf("warning : overlfow on input\n");
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expand(s, t, SIZE);
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printf("%s\n", t);
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return 0;
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}
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/* macro for checking overlfow of t in expand(s, t, n) */
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#define CHECK_OVERFLOW(i, n) \
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do { \
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if (i >= n-1) { \
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printf("warning : overflow in expand\n"); \
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goto terminate; \
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} \
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} while (0)
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/* expand: expand a-z from s to to abc...xyz in t (of size n), same for
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* digits and uppercase letters */
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void expand(char *s, char *t, int n)
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{
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int i = 0;
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if (*s == '\0')
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goto terminate;
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int c;
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for (t[i++] = *(s++); *s != '\0'; s++, i++) {
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if (*s == '-' && IS_RANGE(*(s-1), *(s+1))) {
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for (c = *(s-1) + 1; c < *(s+1); c++, i++) {
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CHECK_OVERFLOW(i, n);
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t[i] = c;
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}
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s++;
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}
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CHECK_OVERFLOW(i, n);
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t[i] = *s;
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}
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terminate:
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t[i] = '\0';
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}
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/* getstr: copies stdin to array s of length n, returns size of string or
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* -1 if overflow */
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int getstr(char *s, int n)
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{
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int i, c;
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for (i = 0; (c = getchar()) != EOF; i++) {
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if (i >= n-1) {
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s[i] = '\0';
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return -1;
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}
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s[i] = c;
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}
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s[i] = '\0';
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return i;
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}
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <string.h>
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#include <limits.h>
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void itoa(int n, char s[]);
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/* passes arg to itoa or INT_MIN if no arg is given */
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int main(int argc, char *argv[])
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{
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int n;
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if (argc < 2) {
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printf("expected : %d\n", INT_MIN);
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n = INT_MIN;
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} else
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n = atoi(argv[1]);
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char s[(int)log10(INT_MAX) + 3];
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itoa(n, s);
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printf("%s\n", s);
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return 0;
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}
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void reverse(char *s);
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/* itoa: convert n to characters in s */
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void itoa(int n, char s[])
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{
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int i;
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unsigned absn = (n < 0) ? -n : n; /* handles INT_MIN */
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i = 0;
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do {
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s[i++] = absn % 10 + '0';
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} while ((absn /= 10) > 0);
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if (n < 0)
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s[i++] = '-';
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s[i] = '\0';
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reverse(s);
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}
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/* reverse: reverses string s in place */
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void reverse(char *s)
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{
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char c, *s2;
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for (s2 = s + strlen(s) - 1; s < s2; s++, s2--)
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c = *s, *s = *s2, *s2 = c;
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}
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#include <stdio.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <math.h>
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#include <string.h>
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void itob(int n, char *s, unsigned b);
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/* passes args to itob, n defaults to INT_MIN, base defaults to 10 */
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int main(int argc, char *argv[])
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{
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int n, b;
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n = (argc > 1) ? atoi(argv[1]) : INT_MIN;
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b = (argc > 2) ? atoi(argv[2]) : 10;
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if (b <= 0) {
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printf("error : invalid base %d\n", b);
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return 1;
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}
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char s[(int)log10(INT_MAX) + 3]; /* +3 for sign and \0 */
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itob(n, s, b);
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printf("%s\n", s);
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return 0;
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}
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void reverse(char *s);
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/* itob: converts int n to string in base b and writes it to s */
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void itob(int n, char *s, unsigned b)
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{
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unsigned un;
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if (n < 0) {
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un = -n;
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*(s++) = '-';
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} else
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un = n;
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char d, *sc = s;
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do {
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d = un % b;
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*(sc++) = d + ((d > 9) ? 'a' - 10 : '0');
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} while ((un /= b) > 0);
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*sc = '\0';
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reverse(s);
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}
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/* reverse: reverses string s in place */
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void reverse(char *s)
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{
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char c, *s2;
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for (s2 = s + strlen(s) - 1; s < s2; s++, s2--)
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c = *s, *s = *s2, *s2 = c;
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}
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <string.h>
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#include <limits.h>
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void itoa(int n, char s[], unsigned w);
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/* passes args to itoa or INT_MIN if no arg is given */
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int main(int argc, char *argv[])
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{
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int n, w;
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n = (argc > 1) ? atoi(argv[1]) : INT_MIN;
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w = (argc > 2) ? atoi(argv[2]) : (int)log10(abs(n)) + 1 + (n < 0);
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if (w < 0) {
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printf("error : invalid width %d\n", w);
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return 1;
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}
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char s[w+1];
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itoa(n, s, w);
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printf("%s\n", s);
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return 0;
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}
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void reverse(char *s);
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/* itoa: convert n to characters (base 10) in s, pads with leading spaces
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* to width w, truncates (left part) string of n if its is wider than w */
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void itoa(int n, char s[], unsigned w)
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{
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int i = 0;
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unsigned un = (n < 0) ? -n : n;
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/* handle zero */
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if (!n && w)
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s[i++] = '0';
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/* handle number */
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for (; i < w && un > 0; un /= 10, i++) {
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s[i] = un % 10 + '0';
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}
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/* handle sign */
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if (n < 0 && i < w)
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s[i++] = '-';
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/* pad with spaces */
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while (i < w)
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s[i++] = ' ';
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s[i] = '\0';
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reverse(s);
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}
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/* reverse: reverses string s in place */
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void reverse(char *s)
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{
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char c, *s2;
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for (s2 = s + strlen(s) - 1; s < s2; s++, s2--)
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c = *s, *s = *s2, *s2 = c;
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}
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