代码

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

评测结果