代码

int binary_search(const unsigned *a, int n, register unsigned x) {
    register const unsigned *l = a, *r = a + n, *m;
    while (l + 1 != r) {
        m = l + ((r - l) >> 1);
        (*m > x) ? (r = m) : (l = m);
    }
    return l - a;
}

评测结果