binarysearch1 binarysearch2 binarysearch3

#include <stdio.h>
static int binarysearch1(int *a, int n, int key) {
  for (int left = 0, right = n - 1, mid = left + (right - left) / 2;
       left <= right; mid = left + (right - left) / 2) {
    if (key < a[mid]) {
      right = mid - 1;
    } else if (a[mid] < key) {
      left = mid + 1;
    } else {
      return mid;
    }
  }
  return -1;
}
static int binarysearch2(int *a, int n, int key) {
  int i = binarysearch1(a, n, key);
  if (i == -1) {
    return -1;
  }
  for (int j = i; 0 <= j; --j) {
    if (a[j] < key) {
      return j + 1;
    }
  }
  return 0;
}
static int binarysearch3(int *a, int n, int key) {
  for (int left = 0, right = n - 1, mid = left + (right - left) / 2;
       left <= right; mid = (right - left) / 2) {
    if (key < a[mid]) {
      right = mid - 1;
    } else if (a[mid] < key) {
      left = mid + 1;
    } else if (mid == 0 || (0 < mid && a[mid - 1] < key)) {
      return mid;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}
int main(void) {
  int a[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
  size_t n = sizeof(a) / sizeof(a[0]);
  {
    printf("%d\n", binarysearch1(a, n, 1));
    printf("%d\n", binarysearch2(a, n, 1));
    printf("%d\n", binarysearch3(a, n, 1));
  }
}