C++实训--矩阵乘法

重要知识点：C++中路径要用“\\”，不然会报错
例如： ifstream in ("C:\\Users\\admin\\Desktop\\123.txt")
矩阵乘法A(m×k) * B(k×n)=C(m×n)

方法一：使用文件流fstream读入矩阵数据

#include<iostream>
#include<fstream>
using namespace std;
void multiply(int **A, int **B, int **C, int m, int k, int n)//C[m][n]=A[m][k]*B[k][n]
{
    for (int i = 0; i < m; i++)
    {
        for (int j = 0; j < n; j++)
        {
            int s = 0;
            for (int x = 0; x < k; x++)
            {
                s += A[i][x] * B[x][j];
            }
            C[i][j] = s;
        }
    }
}
void DynamicCreate2Array(int **&p, int m, int n)//动态创建二维数组
{
    //动态开辟空间
    p = new int*[m]; //开辟行
    for (int i = 0; i < m; i++)
        p[i] = new int[n]; //开辟列

}
void delete2Array(int **p,int m)//释放开辟的资源
{
    for (int i = 0; i < m; i++)
        delete[] p[i];
    delete[] p;
}
void read(int **M, int row, int col, ifstream &infile) //从文件中读入矩阵初始化数据
{
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            infile >> M[i][j];
        }
    }
}
void show(int **M, int row, int col)//显示矩阵
{//raw行 col列

    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cout << M[i][j]<<" ";
            
        }
        cout << endl;
    }
}

int main() {

    ifstream in("C:\\Users\\admin\\Desktop\\123.txt");//路径必须用“\\”
    int m, k, n;
    cout << "请输入m,k,n:" << endl;
        cin >> m >> k >> n;
    int **A, **B, **C;
    cout << "矩阵A：" << endl;
        DynamicCreate2Array(A, m, k);//开辟二维数组A 
        read(A, m, k, in);//从文件中读入矩阵A初始化数据
        show(A, m, k);//显示矩阵
    cout << "矩阵B：" << endl;
        DynamicCreate2Array(B, k, n);
        read(B, k, n, in);
        show(B, k, n);
    cout << "矩阵乘法C=A*B" << endl;
    cout << "矩阵C：" << endl;
        DynamicCreate2Array(C, m, n);
        multiply(A, B, C, m, k, n);
        show(C, m, n);
    delete2Array(A, m);
    delete2Array(B, k);
    delete2Array(C, m);
    system("pause");
    return 0;
}

123.txt
测试结果

方法二：手动输入矩阵数据

#include<iostream>
#include<fstream>
using namespace std;
void multiply(int **A, int **B, int **C, int m, int k, int n)//C[m][n]=A[m][k]*B[k][n]
{
    for (int i = 0; i < m; i++)
    {
        for (int j = 0; j < n; j++)
        {
            int s = 0;
            for (int x = 0; x < k; x++)
            {
                s += A[i][x] * B[x][j];
            }
            C[i][j] = s;
        }
    }
}
void DynamicCreate2Array(int **&p, int m, int n)//动态创建二维数组
{
    //动态开辟空间
    p = new int*[m]; //开辟行
    for (int i = 0; i < m; i++)
        p[i] = new int[n]; //开辟列

}
void delete2Array(int **p,int m)//释放开辟的资源
{
    for (int i = 0; i < m; i++)
        delete[] p[i];
    delete[] p;
}
void init(int **M, int row, int col) //初始化数组
{    //raw行 col列
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cin >> M[i][j];
        }
    }
}
void show(int **M, int row, int col)//显示矩阵
{//raw行 col列

    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < col; j++)
        {
            cout << M[i][j]<<" ";
            
        }
        cout << endl;
    }
}
int main() {

    int m, k, n;
    cout << "请输入m,k,n:" << endl;
        cin >> m >> k >> n;
    int **A, **B, **C;
    cout << "矩阵A：" << endl;
        DynamicCreate2Array(A, m, k);
        init(A, m, k);
    cout << "矩阵B：" << endl;
        DynamicCreate2Array(B, k, n);
        init(B, k, n);
    cout << "矩阵乘法C=A*B" << endl;
    cout << "矩阵C：" << endl;
        DynamicCreate2Array(C, m, n);
        multiply(A, B, C, m, k, n);
        show(C, m, n);
    delete2Array(A, m);
    delete2Array(B, k);
    delete2Array(C, m);
    system("pause");
    return 0;
}

测试结果