J - Fliptile

https://vjudge.net/contest/278989#problem/J

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int N = 16;
int g[N][N], t[N][N], f[N][N];
int cnt, n, m;
int x[4] = {0, 0, -1, 1};
int y[4] = { -1, 1, 0, 0};

void flip(int i, int j)//翻转
{
    ++cnt, f[i][j] = 1;
    t[i][j] = !t[i][j];
    for(int k = 0; k < 4; ++k)
        if(i + x[k] > -1 && j + y[k] > -1)
            t[i + x[k]][j + y[k]] ^= 1;
}

bool ok(int k)
{
    cnt = 0;
    memcpy(t, g, sizeof(t));
    for(int j = 0; j < m; ++j)
        if(k & (1 << (m - 1 - j)))
            flip(0, j);
    for(int i = 1; i < n; ++i)
        for(int j = 0; j < m; ++j)
            if(t[i - 1][j]) flip(i, j);

    for(int j = 0; j < m; ++j)
        if(t[n - 1][j]) return false;
    return true;
}

int main()
{
    int ans, p;
    while(~scanf("%d%d", &n, &m))
    {
        for(int i = 0; i < n; ++i)
            for(int j = 0; j < m; ++j)
                scanf("%d", &g[i][j]);
        ans = n * m + 1, p = -1;
        for(int i = 0; i < (1 << m); ++i)
            if(ok(i) && cnt < ans)
                ans = cnt, p = i;

        memset(f, 0, sizeof(f));
        if(p >= 0)
        {
            ok(p);
            for(int i = 0; i < n; ++i)
                for(int j = 0; j < m; ++j)
                    printf("%d%c", f[i][j], j < m - 1 ? ' ' : '\n');
        }
        else puts("IMPOSSIBLE");
    }
    return 0;
}