C语言输入两个矩阵并实现矩阵的加法、乘法、转置并计算协方差矩阵

注：本题解使用了动态内存分配，需要在编译时加上参数“-std=c99”

#include <stdio.h>
#include <stdlib.h>

// 矩阵结构体
typedef struct {
    int row;
    int col;
    double **data;
} Matrix;

// 创建矩阵
Matrix createMatrix(int row, int col) {
    Matrix mat;
    mat.row = row;
    mat.col = col;
    mat.data = (double **)malloc(row * sizeof(double *));
    for (int i = 0; i < row; i++) {
        mat.data[i] = (double *)malloc(col * sizeof(double));
    }
    return mat;
}

// 释放矩阵
void freeMatrix(Matrix mat) {
    for (int i = 0; i < mat.row; i++) {
        free(mat.data[i]);
    }
    free(mat.data);
}

// 读取矩阵
void readMatrix(Matrix *mat) {
    for (int i = 0; i < mat->row; i++) {
        for (int j = 0; j < mat->col; j++) {
            scanf("%lf", &mat->data[i][j]);
        }
    }
}

// 打印矩阵
void printMatrix(Matrix mat) {
    for (int i = 0; i < mat.row; i++) {
        for (int j = 0; j < mat.col; j++) {
            printf("%.2lf ", mat.data[i][j]);
        }
        printf("\n");
    }
}

// 矩阵加法
Matrix addMatrix(Matrix mat1, Matrix mat2) {
    Matrix mat = createMatrix(mat1.row, mat1.col);
    for (int i = 0; i < mat1.row; i++) {
        for (int j = 0; j < mat1.col; j++) {
            mat.data[i][j] = mat1.data[i][j] + mat2.data[i][j];
        }
    }
    return mat;
}

// 矩阵乘法
Matrix mulMatrix(Matrix mat1, Matrix mat2) {
    Matrix mat = createMatrix(mat1.row, mat2.col);
    for (int i = 0; i < mat1.row; i++) {
        for (int j = 0; j < mat2.col; j++) {
            double sum = 0;
            for (int k = 0; k < mat1.col; k++) {
                sum += mat1.data[i][k] * mat2.data[k][j];
            }
            mat.data[i][j] = sum;
        }
    }
    return mat;
}

// 矩阵转置
Matrix transpose(Matrix mat) {
    Matrix tm = createMatrix(mat.col, mat.row);
    for (int i = 0; i < mat.row; i++) {
        for (int j = 0; j < mat.col; j++) {
            tm.data[j][i] = mat.data[i][j];
        }
    }
    return tm;
}

// 协方差矩阵
Matrix covMatrix(Matrix mat) {
    Matrix tm = transpose(mat);
    Matrix mean = createMatrix(1, mat.col);
    for (int i = 0; i < mat.col; i++) {
        mean.data[0][i] = 0;
        for (int j = 0; j < mat.row; j++) {
            mean.data[0][i] += mat.data[j][i];
        }
        mean.data[0][i] /= mat.row;
    }
    Matrix cov = createMatrix(mat.col, mat.col);
    for (int i = 0; i < mat.col; i++) {
        for (int j = 0; j < mat.col; j++) {
            double sum = 0;
            for (int k = 0; k < mat.row; k++) {
                sum += (mat.data[k][i] - mean.data[0][i]) * (tm.data[j][k] - mean.data[0][j]);
            }
            cov.data[i][j] = sum / (mat.row - 1);
        }
    }
    freeMatrix(tm);
    freeMatrix(mean);
    return cov;
}

int main() {
    int m, n;
    printf("请输入矩阵1的行数和列数：");
    scanf("%d %d", &m, &n);
    Matrix mat1 = createMatrix(m, n);
    printf("请输入矩阵1的元素：\n");
    readMatrix(&mat1);
    printf("请输入矩阵2的行数和列数：");
    scanf("%d %d", &m, &n);
    Matrix mat2 = createMatrix(m, n);
    printf("请输入矩阵2的元素：\n");
    readMatrix(&mat2);

    printf("矩阵1的元素为：\n");
    printMatrix(mat1);
    printf("矩阵2的元素为：\n");
    printMatrix(mat2);

    Matrix mat = addMatrix(mat1, mat2);
    printf("矩阵1和矩阵2的和为：\n");
    printMatrix(mat);
    freeMatrix(mat);

    mat = mulMatrix(mat1, mat2);
    printf("矩阵1和矩阵2的积为：\n");
    printMatrix(mat);
    freeMatrix(mat);

    mat = transpose(mat1);
    printf("矩阵1的转置为：\n");
    printMatrix(mat);
    freeMatrix(mat);

    mat = covMatrix(mat1);
    printf("矩阵1的协方差矩阵为：\n");
    printMatrix(mat);
    freeMatrix(mat);

    freeMatrix(mat1);
    freeMatrix(mat2);
    return 0;
}