202006-2 稀疏向量

注意数据内积可能溢出，需要使用long long

#include <iostream>
#include <unordered_map>

using namespace std;

int main() {

    int n,a,b;
    cin >> n >> a >>b;

    unordered_map<int,int> a_map;

    int index,value;
    for (int i = 0; i < a; i++) {

        cin >> index >>value;
        a_map.insert(make_pair(index,value));
    }

    long long muti = 0;

    for (int j = 0; j < b; j++) {
        cin >> index >>value;
        auto it = a_map.find(index);
        if(it != a_map.end()){
            muti += it->second * value;
        }
    }

    cout << muti <<endl;

    return 0;
}

标签：map,index,int,稀疏,value,cin,202006,long,向量
来源： https://blog.csdn.net/JUandjuddd/article/details/118861639