题解 | 大整数哈希

#include <iostream>
#include<cmath>
#include <map>
using namespace std;

const unsigned long long mod=-1;

int main() {
    int n;
    cin>>n;

    map<unsigned long long, unsigned long long> hash;
    unsigned long long ans=0;
    hash[1] = 0;
    for(int i=1;i<=n;i++){
        unsigned long long x, y;
        cin>>x>>y;

        ans+=(i*hash[x])%mod;
        ans%=mod;

        hash[x] = y;
    }
    cout<<ans;
}
// 64 位输出请用 printf("%lld")