求助大佬，为何死循环

#include<bits/stdc++.h>
using namespace std;
int ansx[14],ansy[14],n;
bool t[14][14];
int keyx = 1, keyy = 1;
int fx[2] = {-1,1};
void dfs(int x,int y)
{
    if(y == n && !t[x][y])
    {
        cout << 1;
        ansx[keyx] = x;
        ansy[keyy] = y;
        keyx++;
        keyy++;
        return;
    }
    if(!t[x][y])
    {
        cout << 1;
        t[x][y] = true;
        for(int i = y; i <= n; i++) t[x][i] = true;
        int key = x;
        for(int i = y; i <= n && x >= 0; i++)
        {
            x += fx[0];
            t[x][i] = true;
        }
        x = key;
        for(int i = y; i <= n && x <= n; i++)
        {
            x += fx[1];
            t[x][i] = true;
        }
    }
    if(x == n && y < n) dfs(1,y+1);
    else dfs(x+1,y);
    return;
}
int main()
{
    cin >> n;
    for(int i = 1; i <= n; i++)
    {
        dfs(i,1);
        for(int k = 1; k <= 13; k++)
            for(int j = 1; j <= 13; j++)
                t[k][j] = false;
    }
    for(int i = 1; i <= keyx; i++) cout << ansx[i] << " ";
    cout << endl;
    for(int i = 1; i <= keyy; i++) cout << ansy[i] << " ";
    return 0;
}