如何使用递归建立螺旋方阵？

#include <stdio.h>void build_matrix(int msize, int a[msize][msize], int size, int value){    int i, row, col;    if(size < 1)        return;    row = col = (msize - size) / 2;    if(size==1){        a[row][col] = value;        return;    }    for(i=0;i<size-1;++i)        a[row][col++] = value++;//RIGHT    for(i=0;i<size-1;++i)        a[row++][col] = value++;//DOWN    for(i=0;i<size-1;++i)        a[row][col--] = value++;//LEFT    for(i=0;i<size-1;++i)        a[row--][col] = value++;//UP    build_matrix(msize, a, size-2, value);}int main(){    int size;    printf("input size : ");    scanf("%d", &size);    int a[size][size];    build_matrix(size, a, size, 1);    for(int r=0;r<size;++r){        for(int c=0;c<size;++c) printf("%3d ", a[r][c]);        printf("n");    }    return 0;}