例：3*3矩阵转置
将二维数组传入函数
(*val)[n]，数组指针
顾名思义，就是指向数组的指针。
每个元素是一个一维数组
c语言 数组与指针 - 时空云博客 (skyw.cc)

#include "stdio.h"
void Transpose(int (*matrix)[3]) 
{
    int tmp;
    // 1,2
    tmp = matrix[0][1];
    matrix[0][1] = matrix[1][0];
    matrix[1][0] = tmp;
    // 1,3
    tmp = matrix[0][2];
    matrix[0][2] = matrix[2][0];
    matrix[2][0] = tmp;
    // 2,3
    tmp = matrix[1][2];
    matrix[1][2] = matrix[2][1];
    matrix[2][1] = tmp;
}
int main() 
{
    int i, j, a[3][3];
    for (i = 0; i < 3; i++) 
    {
        for (j = 0; j < 3; j++) 
        {
            scanf("%d", &a[i][j]);
        }
    }
    Transpose(a);
    for (i = 0; i < 3; i++) 
    {
        for (int j = 0; j < 3; j++) 
        {
            printf("%d ", a[i][j]);
        }
        printf("n");
}
return 0;
}

一级指针表示二维数组

#include <stdio.h>
#define ROW 3
#define COL 3
/* Function declarations */
void matrixInput(int* mat) 
{
    for (int i = 0; i < ROW; i++) 
    {
        for (int j = 0; j < COL; j++) 
        {
            scanf("%d", mat + i * COL + j);
        }
    }
}
void matrixPrint(int* mat) 
{
    for (int i = 0; i < ROW; i++) 
    {
        for (int j = 0; j < COL; j++) 
        {
            printf("%d ", *(mat + i * COL + j));
        }
        printf("n");
    }
}
void matrixMultiply(int* mat1, int* mat2, int* res) {
    //第一个矩阵第i行
    int val;
    for (int i = 0; i < ROW; i++) {
        //第一个矩阵第j列
        for (int j = 0; j < COL; j++) {
            val = *(mat1 + i * COL + 0) * *(mat2 + 0 * COL + j) + *(mat1 + i * COL + 1) * *(mat2 + 1 * COL + j) + *(mat1 + i * COL + 2) * *(mat2 + 2 * COL + j);
            *(res + i * COL + j) = val;
        }
    }
}
int main()
{
    int mat1[ROW][COL];
    int mat2[ROW][COL];
    int product[ROW][COL];
    /*
     * Input elements in matrices.
     */
    // printf("Enter elements in first matrix of size %dx%dn", ROW, COL);
    matrixInput(mat1);
    // printf("Enter elements in second matrix of size %dx%dn", ROW, COL);
    matrixInput(mat2);
    // Call function to multiply both matrices
    matrixMultiply(mat1, mat2, product);
    // Print product of both matrix
    matrixPrint(product);
    return 0;
}