代码

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

评测结果