代码

int binary_search(const unsigned *a, int n, unsigned x)
{
	int l = 0, r = n - 1, mid = (l + r) / 2;

    while (l < r - 1) {
        if (x > a[mid]) l = mid;
        else r = mid;
        mid = (l + r) / 2;
    }
    if (x > a[mid]) {
        while (mid < n) {
            if (x > a[mid]) mid++;
            else break;
        }
        return mid;
    }
    else {
        if (x == a[mid]) return mid;
        while (mid >= 0) {
            if (x < a[mid]) mid--;
            else break;
        }
        return mid;
    }
}

评测结果