核心搜索顺序就是枚举每个位置放/不放

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 10;
int row[N],col[N],dg[N*2],udg[N*2];
int n;
char g[N][N];

void dfs(int x,int y,int sum)
{
    if(y == n)x++,y = 0;
    if(x == n)
    {
        if(sum == n)
        {
            for (int i = 0; i < n; i ++ )puts(g[i]);
            puts("");
        }
        return;
    }

    //不放
    dfs(x,y+1,sum);

    //放
    if(!row[x] && !col[y] && !dg[y-x+n] && !udg[x+y])
    {
        row[x] = col[y] = dg[y-x+n] = udg[x+y] = true;
        g[x][y] = 'Q';
        dfs(x,y+1,sum+1);
        g[x][y] = '.';
        row[x] = col[y] = dg[y-x+n] = udg[x+y] = false;
    }

}
int main()
{
    cin>>n;
    for(int i = 0;i<n;i++)
    {
        for(int j = 0;j<n;j++)g[i][j] = '.';
    }

    dfs(0,0,0);
    return 0;
}