把矩形中的元素蛇形打印出来

#include<stdio.h>
int main()
{
int a[4][3] = {1,2,3,4,5,6,7,8,9,10,11,12};
int row = 4;
int col = 3;
int k = 0;
int num = 0;
for(; num<row*col;)
{
int i = k;
int j = k;
while(j<col-k && num<12)
{
printf("%d ",a[i][j]);
j++;
++num;
}
--j;
++i;
while(i<row-k && num<12)
{
printf("%d ",a[i][j]);
i++;
++num;
}
--i;
--j;
while(j>=k && num<12)
{
printf("%d ",a[i][j]);
j--;
++num;
}
++j;
--i;
while(i>k && num<12)

{
printf("%d ",a[i][j]);
i--;
++num;
}
++k;

}
return 0;
}