C 程序：使用多维数组将两个矩阵相乘

原文： https://www.programiz.com/c-programming/examples/matrix-multiplication

在此示例中，您将学习将两个矩阵相乘并使用用户定义的函数进行显示。

要理解此示例，您应该了解以下 C 编程主题：

• C 数组
• C 多维数组

该程序要求用户输入两个矩阵的大小（行和列）。

为了将两个矩阵相乘，第一个矩阵的列数应等于第二个矩阵的行数。

下面的程序要求两个矩阵的行数和列数，直到满足上述条件。

然后，执行两个矩阵的相乘，结果显示在屏幕上。

为此，我们创建了三个函数：

• enterData() - 从用户那里获取矩阵元素。
• multiplyMatrices() - 将两个矩阵相乘。
• display() - 显示相乘后的结果矩阵。

通过将矩阵传递给函数来相乘

#include <stdio.h>
void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2);
void multiplyMatrices(int first[][10], int second[][10], int multResult[][10], int r1, int c1, int r2, int c2);
void display(int mult[][10], int r1, int c2);
int main() {
    int first[10][10], second[10][10], mult[10][10], r1, c1, r2, c2;
    printf("Enter rows and column for the first matrix: ");
    scanf("%d %d", &r1, &c1);
    printf("Enter rows and column for the second matrix: ");
    scanf("%d %d", &r2, &c2);
    // Taking input until columns of the first matrix is equal to the rows of the second matrix
    while (c1 != r2) {
        printf("Error! Enter rows and columns again.\n");
        printf("Enter rows and columns for the first matrix: ");
        scanf("%d%d", &r1, &c1);
        printf("Enter rows and columns for the second matrix: ");
        scanf("%d%d", &r2, &c2);
    }
    // Function to take matrices data
    enterData(first, second, r1, c1, r2, c2);
    // Function to multiply two matrices.
    multiplyMatrices(first, second, mult, r1, c1, r2, c2);
    // Function to display resultant matrix after multiplication.
    display(mult, r1, c2);
    return 0;
}
void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2) {
    printf("\nEnter elements of matrix 1:\n");
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c1; ++j) {
            printf("Enter a%d%d: ", i + 1, j + 1);
            scanf("%d", &first[i][j]);
        }
    }
    printf("\nEnter elements of matrix 2:\n");
    for (int i = 0; i < r2; ++i) {
        for (int j = 0; j < c2; ++j) {
            printf("Enter b%d%d: ", i + 1, j + 1);
            scanf("%d", &second[i][j]);
        }
    }
}
void multiplyMatrices(int first[][10], int second[][10], int mult[][10], int r1, int c1, int r2, int c2) {
    // Initializing elements of matrix mult to 0.
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            mult[i][j] = 0;
        }
    }
    // Multiplying first and second matrices and storing in mult.
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            for (int k = 0; k < c1; ++k) {
                mult[i][j] += first[i][k] * second[k][j];
            }
        }
    }
}
void display(int mult[][10], int r1, int c2) {
    printf("\nOutput Matrix:\n");
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            printf("%d  ", mult[i][j]);
            if (j == c2 - 1)
                printf("\n");
        }
    }
}

输出

Enter rows and column for the first matrix: 2
3
Enter rows and column for the second matrix: 3
2
Enter elements of matrix 1:
Enter a11: 3
Enter a12: -2
Enter a13: 5
Enter a21: 3
Enter a22: 0
Enter a23: 4
Enter elements of matrix 2:
Enter b11: 2
Enter b12: 3
Enter b21: -9
Enter b22: 0
Enter b31: 0
Enter b32: 4
Output Matrix:
24  29
6  25