代码

int binary_search(const unsigned *a, int n, unsigned x)
{
unsigned long long L = 0, R = 100000000 - 1;
	for(; L < R; ) {
unsigned long long md = (R * (x - a[L]) + L * (a[R] - x)) / (a[R] - a[L]);
if(a[md] == x) return md; else if(a[md] < x) L = md + 1; else R = md - 1;
}
	return L;
}

评测结果