版权声明:嘤嘤嘤 https://blog.csdn.net/HNUCSEE_LJK/article/details/88597397
传送门:POJ 1321 棋盘问题
回溯暴力搜索也不会超时。下次补一下状态压缩dp的做法...
#include <iostream>
#include <string.h>
using namespace std;
int n, k, ans = 0;
int vis[10][10];
int read()
{
cin >> n >> k;
if(n == -1 && k == -1) return 0;
memset(vis, 0, sizeof(vis));
for(int i = 0; i < n; ++i)
{
for(int j = 0; j < n; ++j)
{
char c;
cin >> c;
if(c == '.')
vis[i][j] = -1;
}
}
return 1;
}
int check(int x, int y)
{
if(vis[x][y]) return 0;
for(int j = 0; j < n; ++j)
if(vis[x][j] == 1)
return 0;
return 1;
}
void dfs(int cur, int r)
{
if(!r)
{
++ans;
return;
}
if(cur >= n) return;
for(int i = 0; i < n; ++i)
{
if(check(i, cur))
{
vis[i][cur] = 1;
dfs(cur+1, r-1);
vis[i][cur] = 0;
}
}
dfs(cur+1, r);
}
void solve()
{
ans = 0;
dfs(0, k);
cout << ans << '\n';
}
int main()
{
while(read())
solve();
return 0;
}