代码

int binary_search(const unsigned *a, int n, unsigned x) {
  register int l = 0, r = n - 1;
  register int mid;
  while (l <= r) {
    mid = (l + r) >> 1;
    if (a[mid] == x) break;
    if (a[mid] > x) r = mid - 1;
    if (a[mid] < x) l = mid + 1;
  }
  return mid;
}

评测结果