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  • 矩阵乘法模板

    #include<cstdio>
    #include<cstdlib>
    #include<cstring>
    #include<algorithm>
    using namespace std;
    
    const int inf = 0x3f3f3f3f;
    const int N = 101;
    
    int n, m; 
    struct Matrix{
        int mat[N][N];
        Matrix(){
            memset(mat,0,sizeof(mat));    
        }
        void input(){
            for(int i = 0; i < m; i++)
                for(int j = 0; j < m; j++)
                    scanf("%d",&mat[i][j] );
        }    
        void unit(){
            memset(mat,0,sizeof(mat));
            for(int i = 0; i < m; i++) mat[i][i] = 1;
        } 
        Matrix& operator = (const Matrix &a){
            memcpy( mat, a.mat, sizeof(a.mat));
            return *this;
        } 
        friend Matrix operator * (const Matrix &a, const Matrix &b){
            Matrix res; 
            for(int i = 0; i < m; i++)
                for(int k = 0; k < m; k++)
                    if( a.mat[i][k] )
                        for(int j = 0; j < m; j++)
                            res.mat[i][j] += a.mat[i][k]*b.mat[k][j];
            return res;
        }
        friend bool operator == (const Matrix &a, const Matrix &b){
            for(int i = 0; i < m; i++)
                for(int j = 0; j < m; j++)
                    if( a.mat[i][j] != b.mat[i][j] ) return false;
            return true;
        }  
        friend Matrix operator ^ (Matrix a,int k){
            Matrix res; res.unit();
            Matrix x; memcpy( x.mat, a.mat, sizeof(a.mat));
            while(k){
                if( k&1 ) res = res*x;
                x = x*x; k >>= 1;    
            }    
            return res;
        } 
    };
    
    int dis[N][N];
    Matrix A[N];
    
    void floyd(){
        for(int k = 0; k < n; k++)
        for(int i = 0; i < n; i++) 
        if( dis[i][k] != inf )
        for(int j = 0; j < n; j++)
        if( dis[i][j] > dis[i][k] + dis[k][j] )
        dis[i][j] = dis[i][k] + dis[k][j]; 
    }
    int main(){
        while( scanf("%d%d", &n,&m), n+m ){
            for(int i = 0; i < n; i++)
                A[i].input();
            memset(dis, 0x3f, sizeof(dis));
            for(int i = 0; i < n; i++)
                for(int j = 0; j < n; j++){
                    Matrix t = A[i]*A[j];
                    for(int k = 0; k < n; k++)
                        if( t == A[k] && (k!=i && k!=j) )//不明觉厉... 
                            dis[i][k] = 1;
                }
            floyd();
            
            int a, b, k;scanf("%d", &k);
            for(int i = 0; i < k; i++){
                scanf("%d%d",&a,&b);
                if( dis[a-1][b-1] == inf ) printf("Sorry\n");
                else     printf("%d\n", dis[a-1][b-1] );    
            }
            
        } 
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/yefeng1627/p/3036788.html
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