str.c

#include"stdio.h"
#include"string.h"

size_t bisect(char **a, int len, char *elem) {
    size_t hi = len - 1;
    size_t lo = 0;
    size_t mid;

    while (1) {
        mid = (hi + lo) >> 1;
        int cmp = strcmp(a[mid], elem);
        if (cmp == 0) return mid;
        else if (cmp > 0) hi = mid - 1;
        else lo = mid + 1;

        if (hi == lo) {
            return (strcmp(a[hi], elem) == 0) ? hi : -1;
        }
    }
}

int main() {
    char store[5][5] = {"1234", "2345", "3456", "4567", "5678"};
    char (*a)[5];

    for (int i = 0; i < 5; i++) {
        a[i] = store + i;
    }
}