一道求转置矩阵的问题：我是这样写的，但总是求不出答案，有请网友帮助并详细给解释下，谢谢！
main()
{int a[3][4]={2,4,5,8,6,3,7,1,4,9,0,6},b[4][3],k,j;
for (k=0;k<3;k++)
for (j=0;j<4;j++)
a[k][j]=b[j][k];
printf ("A is :\n");
for (k=0;k<3;k++)
{for (j=0;j<4;j++)
printf ("%4d",a[k][j]);printf("\n");}
printf ("XXA is :\n");
for (k=0;k<4;j++)
{for (j=0;j<3;j++)
printf ("%4d",b[k][j]);printf("\n");}
}

#include<stdio.h>

int main(void)
{
int a[3][4]={2,4,5,8,6,3,7,1,4,9,0,6},b[4][3],k,j;
for (k=0;k<3;k++)
for (j=0;j<4;j++)
b[j][k]=a[k][j];
printf ("A is :\n");
for (k=0;k<3;k++)
{
for (j=0;j<4;j++)
printf ("%4d",a[k][j]);
printf("\n");
}
printf ("XXA is :\n");
for (j=0;j<4;j++)
{
for (k=0;k<3;k++)
printf ("%4d",b[j][k]);
printf("\n");
}
}