poj3740

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 20
#define maxm 305

int n, m;
int map[maxn][maxm];
int num[maxn];
bool g[maxn][maxn];
int rownum[maxn];
bool found;

void input()
{
     
    memset(num, 0, sizeof(num));
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
        {
     
int a;
            scanf("%d", &a);
if (a == 0)
                map[i][j] = 0;
else
            {
     
                map[i][j] = 1;
                num[i]++;
            }
        }
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
        {
     
bool ok = true;
for (int k = 0; k < m; k++)
if (map[i][k] && map[j][k])
                {
     
                    ok = false;
break;
                }
if (ok)
                g[i][j] = true;
else
                g[i][j] = false;
        }
}

void dfs(int tot, int now, int ans)
{
     
if (found)
return;
if (now == n)
    {
     
if (ans == m)
            found = true;
return;
    }
    dfs(tot, now + 1, ans);
bool ok = true;
for (int i = 0; i < tot; i++)
if (!g[rownum[i]][now])
        {
     
            ok = false;
break;
        }
if (ok)
    {
     
        rownum[tot] = now;
        dfs(tot + 1, now + 1, ans + num[now]);
    }
}

int main()
{
     
//freopen("t.txt", "r", stdin);
    while (scanf("%d%d", &n, &m) != EOF)
    {
     
        found = false;
        input();
        dfs(0, 0, 0);
if (found)
            printf("Yes, I found it\n");
else
            printf("It is impossible\n");
    }
return 0;
}