代码

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

评测结果