题解 | 大整数哈希

#include <iostream>
using namespace std;
#include<map>
#include<unordered_map>
#include<vector>
int main() {
   unsigned long long n;
    cin>>n;
    unordered_map<unsigned long long,unsigned long long>m;//x  F(x)
    vector< unsigned long long>ans;
    for( unsigned long long i=0;i<n;i++){
         unsigned long long x,y;
        cin>>x>>y;
        if(m.count(x)==0){
            ans.push_back(0);
            m.insert(make_pair(x,y));
        }
        else if(m.count(x)==1){
            ans.push_back(m[x]);
            m[x]=y;
        }
    }
    unsigned long long sum=0;
   for( unsigned long long i=0;i<n;i++){
       sum+=(i+1)*ans[i];
   }
    cout<<sum;
    
}
// 64 位输出请用 printf("%lld")