rt，#2 #3 #4 WA，其它 TLE

#include <iostream>
using namespace std;
int a[10][10];
bool v[10][10], g[10][10], h[10][10];
void dfs(int step){
    if (step > 81){
        for (int i = 1;i <= 9;i++){
            for (int j = 1;j <= 9;j++) cout << a[i][j] << " ";
            cout << endl;
        }
        return;
    }
    int x = step / 9, y = step % 9, z = x / 3 * 3 + y / 3;
    if (a[x][y] != 0) dfs(step + 1);
    else
        for (int i = 1;i <= 9;i++){
            if (v[x][i] || g[y][i] || h[z][i]) continue;
            v[x][i] = g[y][i] = h[z][i] = 1;
            a[x][y] = i;
            dfs(step + 1);
            v[x][i] = g[y][i] = h[z][i] = 0;
            a[x][y] = 0;
        }
}
int main(){
    for (int i = 1;i <= 9;i++)
        for (int j = 1;j <= 9;j++){
            cin >> a[i][j];
            int x = i, y = j, z = i / 3 * 3 + j / 3;
            if (a[i][j] != 0)
                v[x][a[i][j]] = g[y][a[i][j]] = h[z][a[i][j]] = 1;
        }
    dfs(1);
    return 0;
}