B - Catch Overflow! (范围处理)

题目

很容易想到用堆处理，但会有操作使得数值远大于long long.此时灵活将范围缩小，细节见代码。

#include<iostream>
#include<stack>
using namespace std;
typedef long long ll;
const ll Max = pow(2, 32) - 1;
stack<ll> sta;

int main()
{
    
    
	ll a = 0;
	int t;cin >> t;
	ll sum = 1;
	ll ans = 0;
	int f = 0;
	sta.push(1);
	while (t--)
	{
    
    
		string str;cin >> str;
		ll num;
		if (str == "for")
		{
    
    
			cin >> num;
			sum *= num;
			if (sum > Max)sum = Max + 1;
			sta.push(sum);
		}
		if (str == "end")
		{
    
    
			sta.pop();
			sum = sta.top();
		}
		if (str == "add")
		{
    
    
			if (ans+sum > Max) f = 1;
			ans += sum;
		}
	}
	if (f)cout << "OVERFLOW!!!" << endl;
	else cout << ans << endl;
}