C++中int和long long特别容易被忽略的点，在做乘法的时候即使单个变量在int范围内，如果乘积超了int，也需要将乘数定义为longlong 否则会出错
请看示例：

#include <bits/stdc++.h>
using namespace std;

int main(){
	int i = 100000000;
	long long j = 100000000;
	cout << i*i << " " << sizeof(i*i) << " " << (long long)i*i << " " << sizeof((long long)i*i) << " " << i << endl;
	cout << j*j << " " << sizeof(j*j) << " " << int(j*j) << " " << sizeof(int(j*j)) << " " << j << endl;	
	return 0;
}

注意里面类型转换意义不同！
结果：