hdu Matrix Multiplication 写一个类似哈希函数的东西一切就解决了。

Problem Description

You are given three n × n matrices A, B and C. Does the equation A × B = C hold true?

 

Input

The first line of input contains a positive integer n (n ≤ 500) followed by the the three matrices A, B and C respectively. Each matrix's description is a block of n × n integers.

It guarantees that the elements of A and B are less than 100 in absolute value and elements of C are less than 10,000,000 in absolute value.

 

Output

Output "YES" if the equation holds true, otherwise "NO".

 

Sample Input

2 1 0 2 3 5 1 0 8 5 1 10 26

 

Sample Output

YES

***************************************************************************************************************************

#include<iostream>
#include<string>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<queue>
#include<algorithm>
#include<vector>
#define LL long long
using namespace std;

LL a[501][501],b[501][501],c[501][501];
LL d[501],e[501],f[501],x[501];
LL n,m,i,j,k;
int main()
{
    while(scanf("%lld",&n)!=EOF)
    {
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
                scanf("%lld",&a[i][j]);
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
                scanf("%lld",&b[i][j]);
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
                scanf("%lld",&c[i][j]);
        for(i=0; i<n; i++)
            x[i]=i;
        for(i=0; i<n; i++)
            f[i]=e[i]=d[i]=0;
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
            {
                e[i]+=b[i][j]*x[j];
                f[i]+=c[i][j]*x[j];
            }
        for(i=0; i<n; i++)
            for(int j=0; j<n; j++)
                d[i]+=a[i][j]*e[j];
        for(i=0; i<n; i++)
          if(d[i]!=f[i]) break;
        if(i<n)
            puts("NO");
        else
            puts("YES");
    }
    return 0;
}