二维数组：行列互换/求最大值及其所在位置/求各行各列的和/矩阵乘积/深入理解二维数组

二维数组
1.定义 只有行号可以省略，初始化 全部初始化/部分初始化/不初始化
2.元素引用
3.存储形式 :顺序存储 按行存储
4.深入理解二维数组

#include<stdio.h>
#include<stdlib.h>#define M 2
#define N 3int mian()
{int a[M][N] = {{1,2,3},{4,5,6}};//int a[M][N] = {1,2,3}；按顺序赋值int i,j;printf("a = %p\n",a); printf("a = %p\n",a+1); for(i =0;i<M;i++){for (j=0;j<N;j++){printf("%p-->%d",&a[i][j],a[i][j]);}printf("\n");}	exit(0);
}

行列互换

#include<stdio.h>
#include<stdlib.h>#define M 2
#define N 3static void change(void)
{int a[M][N] = {1,2,3,4,5,6},b[N][M];
//错误。数组名是常量 不能放在等号的左边	a = {1,2,3,4};int i,j;for(i =0;i<M;i++){for (j=0;j<N;j++){printf("%d ",a[i][j]);b[j][i] = a[i][j];}printf("\n");}	for(i =0;i<N;i++){for (j=0;j<M;j++){printf("%d ",b[i][j]);}printf("\n");}	
}int main(){change();exit(0);}

求最大值

#include<stdio.h>
#include<stdlib.h>#define M 2
#define N 3static void max(void)
{int a[M][N] = {17,27,3,48,50,66};
//错误。数组名是常量 不能放在等号的左边	a = {1,2,3,4};int i,j;int max = a[0][0],row =0,colum =0;for(i =0;i<M;i++){for (j=0;j<N;j++){if(max <a[i][j]){max =a[i][j];row=i;colum= j;}}}	printf("max:a[%d][%d] =%d ",row,colum,a[row][colum]);
}int main(){//change();max();exit(0);}

求和

#include<stdio.h>
#include<stdlib.h>#define M 5
#define N 4static void sum(void)
{int a[M][N] = {{1,2,3},{4,5,6},{7,8,9},{10,11,12}};int i,j;for(i = 0; i < 4; i++)
{for(j = 0; j < 3; j++){a[4][3] += a[i][j];a[4][j] += a[i][j];a[i][3] += a[i][j];}
}for(i = 0; i < 5; i++){for(j = 0; j < 4; j++){printf("%4d", a[i][j]);}}int main(){//change();//max();sum();exit(0);}

矩阵乘积

#include<stdio.h>
#include<stdlib.h>#define M 2
#define N 3
#define K 2static void mul(void)
{int a[M][N] = {1,2,3,4,5,6};int b[N][K] = {1,0,0,1,1,0};int c[M][K] = {0};int i,j,k;for(i = 0; i < M; i++){for(j = 0; j < K; j++){for(k = 0; k<N; k++)c[i][j] += a[i][k] * b[k][j];}}int main(){//change();//max();//sum();mul();exit(0);}

深入理解二维数组
多个一维数组