方阵填数

N=5
13 14 15 16 1
12 23 24 17 2
11 22 25 18 3
10 21 20 19 4
9 8 7 6 5

const int MAXN = 20;
int a[MAXN][MAXN];
 
int main(int argc, const char * argv[]) {
    int n;
    cin >>n;
     
    int value, x = 0, y = n-1;
    value = a[0][n-1] = 1;
     
    while (value < n*n) {
        while (x+1<n && a[x+1][y]==0)
            a[++x][y] = ++value;
        while (y-1>=0 && a[x][y-1]==0)
            a[x][--y] = ++value;
        while (x-1>=0 && a[x-1][y]==0)
            a[--x][y] = ++value;
        while (y+1<n && a[x][y+1]==0)
            a[x][++y] = ++value;
    }
    for (int i=0; i<n; i++) {
        for (int j =0; j<n; j++) {
            cout <<a[i][j]<<" ";
        }
        cout <<endl;
    }
     
    return 0;
}