diff --git a/k&r/03-control-flow/03-01.c b/k&r/03-control-flow/03-01.c new file mode 100644 index 0000000..d589e20 --- /dev/null +++ b/k&r/03-control-flow/03-01.c @@ -0,0 +1,69 @@ +#include + +#define SIZE 1000000 +#define X 2*((SIZE-1) / 2) + 1 +#define T 10000000 + +int binsearch(int x, int v[], int n); +int binsearch_old(int x, int v[], int n); + +/* run binsearch on array of size SIZE + * if arg is provided use old binsearch */ +int main(int argc, char *argv[]) +{ + long i; + int arr[SIZE]; + + for (i = 0; i < SIZE; ++i) + arr[i] = 2 * i; + + if (argc == 1) { + for (i = 0; i < T; ++i) + binsearch(X, arr, SIZE); + printf("binsearch : %d\n", binsearch(X, arr, SIZE)); + } + else { + for (i = 0; i < T; ++i) + binsearch_old(X, arr, SIZE); + printf("old binsearch : %d\n", binsearch_old(X, arr, SIZE)); + } + return 0; +} + +/* binsearch: find x in sorted v of length n, using one comparison in loop */ +int binsearch(int x, int v[], int n) +{ + int low, high, mid; + + low = 0; + high = n - 1; + while (low < high) { + mid = (low + high) / 2; + if (x <= v[mid]) + high = mid; + else + low = mid + 1; + } + if (v[low] == x) + return low; + return -1; +} + +/* binsearch: find x in sorted v of length n, using two comparisons in loop */ +int binsearch_old(int x, int v[], int n) +{ + int low, high, mid; + + low = 0; + high = n - 1; + while (low <= high) { + mid = (low + high) / 2; + if (x < v[mid]) + high = mid - 1; + else if (x > v[mid]) + low = mid + 1; + else + return mid; + } + return -1; +} diff --git a/k&r/03-control-flow/03-02.c b/k&r/03-control-flow/03-02.c new file mode 100644 index 0000000..6339b51 --- /dev/null +++ b/k&r/03-control-flow/03-02.c @@ -0,0 +1,64 @@ +#include +#include + +#define ESCAPE_SEQS \ + X('\a', 'a') X('\b', 'b') X('\f', 'f') X('\n', 'n') \ + X('\r', 'r') X('\t', 't') X('\v', 'v') + +#define SIZE 1000 + +void escape(char *s, char *t); +void unescape(char *s, char *t); + +/* runs escape and unescape on stdin, prints results*/ +int main() +{ + int i, c; + char s[SIZE+1], t[2*SIZE+1]; + + for (i = 0; (c = getchar()) != EOF; i++) { + if (i >= SIZE) { + printf("warning : buffer overflow\n"); + break; + } + s[i] = c; + } + s[i] = '\0'; + escape(s, t); + printf("--- escaped ---\n%s\n", t); + + unescape(t, s); + printf("\n-- unescaped --\n%s", s); + return 0; +} + +/* escape: makes escape sequences visible as it copies s to t + * size of t must be 2*size of s */ +void escape(char *s, char *t) +{ + for (; *s != '\0'; s++, t++) + switch (*s) { + #define X(e, c) case e : *(t++) = '\\'; *t = c; break; + ESCAPE_SEQS + #undef X + default : *t = *s; break; + } + *t = '\0'; +} + +/* unescape: inverse of escape */ +void unescape(char *s, char *t) +{ + for (; *s != '\0'; s++, t++) { + if (*s == '\\') + switch (*(s+1)) { + #define X(e, c) case c : *t = e; s++; continue; + ESCAPE_SEQS + #undef X + } + *t = *s; + } + *t = '\0'; +} + + diff --git a/k&r/03-control-flow/03-03.c b/k&r/03-control-flow/03-03.c new file mode 100644 index 0000000..369c0c6 --- /dev/null +++ b/k&r/03-control-flow/03-03.c @@ -0,0 +1,75 @@ +#include +#include + +#define SIZE 1000 + +/* check if c1-c2 is valid range */ +#define IS_RANGE(c1, c2) ( \ + (isdigit(c1) && isdigit(c2)) || \ + (islower(c1) && islower(c2)) || \ + (isupper(c1) && isupper(c2)) \ +) + +int getstr(char *s, int n); +void expand(char *s, char *t, int n); + +/* copy stdin to string, run expand, print output */ +int main() +{ + char s[SIZE], t[SIZE]; + if (getstr(s, SIZE) < 0) + printf("warning : overlfow on input\n"); + expand(s, t, SIZE); + printf("%s\n", t); + return 0; +} + +/* macro for checking overlfow of t in expand(s, t, n) */ +#define CHECK_OVERFLOW(i, n) \ + do { \ + if (i >= n-1) { \ + printf("warning : overflow in expand\n"); \ + goto terminate; \ + } \ + } while (0) + +/* expand: expand a-z from s to to abc...xyz in t (of size n), same for + * digits and uppercase letters */ +void expand(char *s, char *t, int n) +{ + int i = 0; + if (*s == '\0') + goto terminate; + + int c; + for (t[i++] = *(s++); *s != '\0'; s++, i++) { + if (*s == '-' && IS_RANGE(*(s-1), *(s+1))) { + for (c = *(s-1) + 1; c < *(s+1); c++, i++) { + CHECK_OVERFLOW(i, n); + t[i] = c; + } + s++; + } + CHECK_OVERFLOW(i, n); + t[i] = *s; + } + terminate: + t[i] = '\0'; +} + +/* getstr: copies stdin to array s of length n, returns size of string or + * -1 if overflow */ +int getstr(char *s, int n) +{ + int i, c; + + for (i = 0; (c = getchar()) != EOF; i++) { + if (i >= n-1) { + s[i] = '\0'; + return -1; + } + s[i] = c; + } + s[i] = '\0'; + return i; +} diff --git a/k&r/03-control-flow/03-04.c b/k&r/03-control-flow/03-04.c new file mode 100644 index 0000000..12c98d7 --- /dev/null +++ b/k&r/03-control-flow/03-04.c @@ -0,0 +1,51 @@ +#include +#include +#include +#include +#include + + +void itoa(int n, char s[]); + +/* passes arg to itoa or INT_MIN if no arg is given */ +int main(int argc, char *argv[]) +{ + int n; + if (argc < 2) { + printf("expected : %d\n", INT_MIN); + n = INT_MIN; + } else + n = atoi(argv[1]); + + char s[(int)log10(INT_MAX) + 3]; + itoa(n, s); + printf("%s\n", s); + return 0; +} + +void reverse(char *s); + +/* itoa: convert n to characters in s */ +void itoa(int n, char s[]) +{ + int i; + unsigned absn = (n < 0) ? -n : n; /* handles INT_MIN */ + + i = 0; + do { + s[i++] = absn % 10 + '0'; + } while ((absn /= 10) > 0); + + if (n < 0) + s[i++] = '-'; + s[i] = '\0'; + reverse(s); +} + +/* reverse: reverses string s in place */ +void reverse(char *s) +{ + char c, *s2; + for (s2 = s + strlen(s) - 1; s < s2; s++, s2--) + c = *s, *s = *s2, *s2 = c; +} diff --git a/k&r/03-control-flow/03-05.c b/k&r/03-control-flow/03-05.c new file mode 100644 index 0000000..1f368ab --- /dev/null +++ b/k&r/03-control-flow/03-05.c @@ -0,0 +1,53 @@ +#include +#include +#include +#include +#include + +void itob(int n, char *s, unsigned b); + +/* passes args to itob, n defaults to INT_MIN, base defaults to 10 */ +int main(int argc, char *argv[]) +{ + int n, b; + n = (argc > 1) ? atoi(argv[1]) : INT_MIN; + b = (argc > 2) ? atoi(argv[2]) : 10; + if (b <= 0) { + printf("error : invalid base %d\n", b); + return 1; + } + + char s[(int)log10(INT_MAX) + 3]; /* +3 for sign and \0 */ + itob(n, s, b); + printf("%s\n", s); + return 0; +} + +void reverse(char *s); + +/* itob: converts int n to string in base b and writes it to s */ +void itob(int n, char *s, unsigned b) +{ + unsigned un; + if (n < 0) { + un = -n; + *(s++) = '-'; + } else + un = n; + + char d, *sc = s; + do { + d = un % b; + *(sc++) = d + ((d > 9) ? 'a' - 10 : '0'); + } while ((un /= b) > 0); + *sc = '\0'; + reverse(s); +} + +/* reverse: reverses string s in place */ +void reverse(char *s) +{ + char c, *s2; + for (s2 = s + strlen(s) - 1; s < s2; s++, s2--) + c = *s, *s = *s2, *s2 = c; +} diff --git a/k&r/03-control-flow/03-06.c b/k&r/03-control-flow/03-06.c new file mode 100644 index 0000000..4b5dc07 --- /dev/null +++ b/k&r/03-control-flow/03-06.c @@ -0,0 +1,62 @@ +#include +#include +#include +#include +#include + + +void itoa(int n, char s[], unsigned w); + +/* passes args to itoa or INT_MIN if no arg is given */ +int main(int argc, char *argv[]) +{ + int n, w; + n = (argc > 1) ? atoi(argv[1]) : INT_MIN; + w = (argc > 2) ? atoi(argv[2]) : (int)log10(abs(n)) + 1 + (n < 0); + + if (w < 0) { + printf("error : invalid width %d\n", w); + return 1; + } + + char s[w+1]; + itoa(n, s, w); + printf("%s\n", s); + return 0; +} + +void reverse(char *s); + +/* itoa: convert n to characters (base 10) in s, pads with leading spaces + * to width w, truncates (left part) string of n if its is wider than w */ +void itoa(int n, char s[], unsigned w) +{ + int i = 0; + unsigned un = (n < 0) ? -n : n; + + /* handle zero */ + if (!n && w) + s[i++] = '0'; + + /* handle number */ + for (; i < w && un > 0; un /= 10, i++) { + s[i] = un % 10 + '0'; + } + /* handle sign */ + if (n < 0 && i < w) + s[i++] = '-'; + /* pad with spaces */ + while (i < w) + s[i++] = ' '; + + s[i] = '\0'; + reverse(s); +} + +/* reverse: reverses string s in place */ +void reverse(char *s) +{ + char c, *s2; + for (s2 = s + strlen(s) - 1; s < s2; s++, s2--) + c = *s, *s = *s2, *s2 = c; +}