矩阵相乘实例：

#include <stdio.h>

// 求 m*k 型矩阵 A 左乘 k*n 型矩阵 B 后的 m*n 型矩阵 C

int main()
{
    struct Matrixs
    {
        int elements[100][100];
        int row;
        int col;
    }matrixA, matrixB, matrixC;

    int m, k, n;
    printf("请输入矩阵A行数和列数：");
    scanf("%d %d", &matrixA.row, &matrixA.col);
    matrixB.row = matrixA.col;//矩阵A的列数等于矩阵B的行数
    printf("请输入矩阵B列数：");
    scanf("%d", &matrixB.col);
    printf("\n输入矩阵A:\n");
    for (m = 0; m < matrixA.row; ++m)
    for (k = 0; k < matrixA.col; ++k)
    {
        printf("请输入元素A(%d,%d):", m+1, k+1);
        scanf("%d", &matrixA.elements[m][k]);
    }

    printf("\n输入矩阵B:\n");
    for (k = 0; k < matrixA.col; ++k)
        for (n = 0; n < matrixB.col; ++n)
        {
            printf("请输入元素B(%d,%d):", k+1, n+1);
            scanf("%d", &matrixB.elements[k][n]);
        }
    for (m = 0; m < matrixA.row; ++m)
        for (n = 0; n < matrixB.col; ++n)
            for (k = 0; k < matrixA.col; ++k)
            {
            if (k == 0) matrixC.elements[m][n] = 0;//为新矩阵C每个元素初始化
                matrixC.elements[m][n] += matrixA.elements[m][k] * matrixB.elements[k][n];
            }
            printf("\n\n矩阵A为：\n\n");
    for (m = 0; m < matrixA.row; ++m)
    {
        printf("  |");
        for (k = 0; k < matrixA.col; ++k)
        {
            printf(" %-5d", matrixA.elements[m][k]);
        }
        printf("\b\b\b|\n");
    }
    printf("\n\n矩阵B为：\n\n");
    for (k = 0; k < matrixB.row; ++k)
    {
        printf("  |");
        for (n = 0; n < matrixB.col; ++n)
        {
            printf(" %-6d", matrixB.elements[k][n]);
        }
        printf("\b\b|\n");
    }

    printf("\n矩阵A左乘矩阵B为：\n\n");
    for (m = 0; m < matrixA.row; ++m)
    {
        printf("  |");
        for (n = 0; n < matrixB.col; ++n)
        {
            printf(" %-6d",matrixC.elements[m][n]);
        }
        printf("\b\b|\n");
    }
    printf("\n");
    return 0;
}