题解 | 大整数哈希

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

unsigned long long n;
unordered_map<unsigned long long,unsigned long long> um;
unsigned long long x,y;

int main(){
	cin>>n;
	unsigned long long res=0;
	for(unsigned long long i=1;i<=n;i++){
		cin>>x>>y;
		unsigned long long ansi=0;
		if(um.count(x)){
			ansi=um[x];
		}
		res+=i*ansi;
		um[x]=y;
	}
	cout<<res<<endl;
    return 0;
}