代码

int binary_search(const unsigned *a, int n, unsigned x)
{
unsigned lo = 0, hi = n;
while (lo < hi) {
unsigned mi = (lo + hi) / 2;
if (a[mi] < x) lo = mi;
else if (a[mi] == x) return mi;
else hi = mi;
}
return 0;  // Oh, -Werror
}

评测结果