malloc二维数组的2种方法

#include <malloc.h>
#include <stdio.h>
int main()
{
    int **a = malloc(sizeof(int)*3);
    a[0]= malloc(sizeof(int)*2);
    a[1]= malloc(sizeof(int)*2);
    a[2]= malloc(sizeof(int)*2);
    a[0][0] =1;
    a[0][1] =2;
    a[1][0] =3;
    a[1][1] = 4;
    a[2][0] =5;
    a[2][1] = 6;
    printf("%d	%d	%d	%d	%d	%d
",a[0][0],a[0][1],a[1][0],a[1][1],a[2][0],a[2][1]); 
    free(a[0]);
    free(a[1]);
    free(a[2]);
    free(a);
}

#include <malloc.h>
#include <stdio.h>
int main()
{
    int (*a)[2] = malloc(sizeof(int)*3*2);
    a[0][0] =1;
    a[0][1] =2;
    a[1][0] =3;
    a[1][1] = 4;
    a[2][0] =5;
    a[2][1] = 6;
    printf("%d	%d	%d	%d	%d	%d
",a[0][0],a[0][1],a[1][0],a[1][1],a[2][0],a[2][1]); 
    free(a);
}