代码

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

评测结果