POJ3276——暴力——Fliptile

/*
枚举第一行所有的状态，接下来的行都已经确定了，字典序最小输出
 */
/************************************************
* Author        :Powatr
* Created Time  :2015-8-9 13:18:38
* File Name     :D.cpp
 ************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int MAXN = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;

int n, m;
char s[400];
char ss[400];
int  maze[20][20];
int mp[20][20];
int path[20][20];
int f_path[20][20];

int solve(int cnt)
{
    int  ans = 0;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            mp[i][j] = maze[i][j];
    for(int i = 1; i <= m; i++){
        if(cnt&(1<<(i-1))){
            ans++;
            path[1][i] ^= 1;
            mp[1][i] ^= 1;
            mp[1][i-1] ^= 1;
            mp[1][i+1] ^= 1;
            mp[2][i] ^= 1;
        }
    } 
    for(int i = 2; i <= n;i++){
        for(int j = 1; j <= m; j++){
            if(mp[i-1][j] == 1){
                ans++;
                path[i][j] ^= 1;
                mp[i-1][j] ^= 1;
                mp[i][j] ^= 1;
                mp[i][j-1] ^= 1;
                mp[i][j+1] ^= 1;
                mp[i+1][j] ^= 1;
            }
        }
    }
       for(int j = 1; j <= m; j++)
           if(mp[n][j])
               return -1;
   return ans;
}

int main(){
    while(~scanf("%d%d", &n, &m)){
        for(int i = 1; i <= n; i++){
            for(int j = 1; j <= m; j++)
                scanf("%d", &maze[i][j]);
            }
        memset(f_path, 0 , sizeof(f_path));
        for(int i = 1; i <= n*m ; i++)
            ss[i] = ‘1‘;
        int min1 = n*m + 1;
        for(int i = 0; i <= (1<<n) - 1; i++){
            int res = 0;
            memset(path, 0, sizeof(path));
            memset(mp, 0, sizeof(mp));
            int temp = solve(i);
            if(temp == -1) continue;
            if(temp <= min1) {
                min1 = temp;
                for(int i = 1; i <= n; i++){
                    for(int j = 1; j <= m; j++){
                        s[++res] = (char)(path[i][j] + ‘0‘);
                    }
                }
                if(strcmp(s+1, ss+1) < 0){
                    strcpy(ss+1, s+1);
                }
            }
        }
        if(min1 == n*m + 1) 
            printf("IMPOSSIBLE\n");
        else {
            for(int i = 1; i <= n*m; i++){
                printf("%c%c", ss[i], i % m == 0 ? ‘\n‘ : ‘ ‘);
            }
        }
    }
    return 0;
}