代码

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

评测结果