POJ3318 Matrix Multiplication

/*
 POJ3318 Matrix Multiplication
 http://poj.org/problem?id=3318
 随机化算法 矩阵
 随机一个1×n的矩阵h
 在ab=c左右两边左乘h
 验证是否相等
 然而不知道为什么g++交就会RE，
 c++交AC
 *
 */
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <iostream>
#include <map>
#include <set>
#include <ctime>
#include <cstdlib>
//#define test
using namespace std;
const int Nmax=505;
const int mod=500;
int n;
struct Matrix
{
    int n,m;
    int num[Nmax][Nmax];
    Matrix()
    {
        n=0;
        m=0;
    }
    Matrix &operator = (const Matrix b)
    {
        n=b.n;
        m=b.m;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                num[i][j]=b.num[i][j];
        //show();
        return *this;
    }
    //Matrix(Matrix &a)
    //{
        //*this=a;
    //}
    Matrix(int _n,int _m,int **_num)
    {
        n=_n;
        m=_m;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                num[i][j]=_num[i][j];
    }
    friend Matrix operator + (Matrix a,Matrix b)
    {
        Matrix ans;
        ans.n=a.n;
        ans.m=a.m;
        for(int i=1;i<=ans.n;i++)
            for(int j=1;j<=ans.m;j++)
                ans.num[i][j]=a.num[i][j]+b.num[i][j];
        return ans;
    }
    friend Matrix operator * (Matrix a,Matrix b)
    {
        Matrix ans;
        if(a.m!=b.n)
        {
            printf("error!
");
            return ans;
        }
        ans.n=a.n,ans.m=b.m;
        int tmp=a.m;
        for(int i=1;i<=ans.n;i++)
            for(int j=1;j<=ans.m;j++)
                ans.num[i][j]=0;
        for(int i=1;i<=ans.n;i++)
            for(int j=1;j<=ans.m;j++ )
                for(int k=1;k<=tmp;k++)
                    ans.num[i][j]+=a.num[i][k]*b.num[k][j];
        //ans.show();
        return ans;
    }
    friend bool operator != (Matrix a,Matrix b)
    {
        if(a.n!=b.n || a.m!=b.m)
            return 1;
        for(int i=1;i<=a.n;i++)
            for(int j=1;j<=a.m;j++)
                if(a.num[i][j]!=b.num[i][j])
                    return 1;
        return 0;
    }
    void show()
    {
        printf("n:%d m:%d
",n,m);
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                printf("%d%c",num[i][j],j==m? '
':' ');
    }
};
Matrix a,b,c,h;
//Matrix tmpa,tmpb,tmpc;
int work()
{
    srand(unsigned(time(0)));
    h.n=1,h.m=n;
    for(int t=1;t<=5;t++)
    {
        for(int i=1;i<=n;i++)
        {
            h.num[1][i]=rand()%mod;

        }
        //h.show();
        //tmpa=h*a;
        //tmpb=tmpa*b;
        //tmpc=h*c;
        //tmpa.show();
        //tmpb.show();
        //tmpc.show();
        if( ( (h*a)*b )!=(h*c) )
            return 0;
    }

    return 1;
}
int main()
{
    #ifdef test
    #endif
    //freopen("poj3318.in","r",stdin);
    scanf("%d",&n);
    a.n=a.m=b.n=b.m=c.n=c.m=n;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            scanf("%d",&a.num[i][j]);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            scanf("%d",&b.num[i][j]);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            scanf("%d",&c.num[i][j]);
    if(work())
        printf("YES
");
    else
        printf("NO
");
    return 0;
}