简单c++拼图游戏疑惑

Question

按了按键之后没有交换

```c++
#include <iostream>
#include <string>
#define N 3
using namespace std;
class game{
private:
    int a[N][N] = {0};
    int i, j;
public:
    void set(){
    //    int i, j;
        for(i = 0; i < N; i++)
        {
            for(j = 0; j < N; j++)
            {
                cin >> a[i][j];
            }
        }
    }
    void display(){
    //    int i, j;
        for(i = 0; i < N; i++)
        {
            for(j = 0; j < N; j++)
            {
                if(a[i][j] == 0)
                {
                    cout << " ";
                }
                else
                {
                    cout << a[i][j] << " ";
                }
            }
            cout << "\n";
        }
    }
    void move(){
        char in = 0;
    //    int i, j;
        char t = 0;
        for(i = 0; i < N; i++)
        {
            for(j = 0; j < N; j++)
            {
                if(a[i][j] == 0)
                {
                break;
                }
    
            }
        }
        cin >> in;
        if(in == 'a'){
            t = a[i][j];
            a[i][j] = a[i][j+1];
            a[i][j+1] = t;
        }
        else if(in == 'd'){
            t = a[i][j];
            a[i][j] = a[i][j-1];
            a[i][j-1] = t;
        }
        else if(in == 'w'){
            t = a[i][j];
            a[i][j] = a[i-1][j];
            a[i-1][j] = t;
        }
        else if(in == 's'){
            t = a[i][j];
            a[i][j] = a[i+1][j];
            a[i+1][j] = t;
        }
    }
    
};
int main()
{
    game a;
    a.set();
    a.display();
    while(1){
        a.move();
        a.display();
        //TODO
    }
    return 0;
}

```

Answer 1

    for(i = 0; i < N; i++)
    {
        for(j = 0; j < N; j++)
        {
            if(a[i][j] == 0)
            {
            break;//没有退出循环
            }
        }
    }