P3405 [USACO16DEC] Cities and States S

P3405 [USACO16DEC] Cities and States S
城市的前两位字符有效，已知字符串均为大写字母构成，故可转26进制储存，不会重复。
city[M][M] 存入：行为国家列为州 若存在与另一组数据对应为city 1 == state 2 && state 1 == city 2；ans++；

点击查看代码

#include<bits/stdc++.h>
using namespace std;
const int M = 702;
int city[M][M] = {0},ans = 0;
int main()
{string x, y;memset(city, 0, sizeof city);int n;cin>>n;while(n--){cin>>x>>y;int q = (x[0]-'A')*26+x[1]-'A';int p = (y[0]-'A')*26+y[1]-'A';if(p != q){city[q][p]++;ans+=city[p][q];}}cout<<ans;
}