矩阵 ACdream1213 Matrix Multiplication

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题意：将一个矩阵A先转置，然后再与原A矩阵相乘，求最后得到的矩阵中的数字之和

思路：刚开始没看懂题目，，，随便写几个矩阵A，然后倒置后相乘找规律，一下子就能发现规律，最后的答案等于每一行数字之和的平方之和

#include<map>#include<set>#include<cmath>#include<stack>#include<queue>#include<cstdio>#include<string>#include<vector>#include<cstring>#include<iostream>#include<algorithm>#include<functional>#define FIN freopen("input.txt","r",stdin)#define FOUT freopen("output.txt","w+",stdout)using namespace std;typedef long long LL;typedef pair<int, int>PII;const int MX = 1e5 + 5;const int INF = 0x3f3f3f3f;int cnt[MX];int main() {    int n, m;//FIN;    while(~scanf("%d%d", &n, &m)) {        memset(cnt, 0, sizeof(cnt));        for(int i = 1; i <= m; i++) {            int u, v;            scanf("%d%d", &u, &v);            if(u != v) {                cnt[u]++; cnt[v]++;            } else cnt[u]++;        }        LL ans = 0;        for(int i = 1; i <= n; i++) {            ans += (LL)cnt[i] * cnt[i];        }        printf("%lld\n", ans);    }    return 0;}

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