题解 | 大整数哈希

#include <iostream>
#include<unordered_map>
using namespace std;

int main() {
    unsigned long long n;
    cin>>n;
    unordered_map<unsigned long long ,unsigned long long> f;
    unsigned long long sum=0;

    for(int i=0;i<n;i++){
        unsigned long long x,y;
        unsigned long long ans;
        cin>>x>>y;
        if(f.count(x)){
            ans = f[x];
            f[x] = y;
        }else{
            ans=0;
            f.emplace(x,y);
        }
        sum+=(i+1)*ans;
    }

    cout<<sum;
}