POJ 3279 Fliptile——开关问题

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

int m, n, a[20][20], b[20][20], c[20][20], ans[20][20];

void fff(int x, int y) {
    b[x][y] = !b[x][y];
    if (x - 1 >= 0) {
        b[x - 1][y] = !b[x - 1][y];
    }
    if (x + 1 < m) {
        b[x + 1][y] = !b[x + 1][y];
    }
    if (y - 1 >= 0) {
        b[x][y - 1] = !b[x][y - 1];
    }
    if (y + 1 < n) {
        b[x][y + 1] = !b[x][y + 1];
    }
}

int main()
{
    while (scanf("%d %d", &m, &n) == 2) {
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                scanf("%d", &a[i][j]);
            }
        }
        int minf = 1000;
        for (int kase = 0; kase < (1<<n); kase++) {
            for (int i = 0; i < m; i++) {
                for (int j = 0; j < n; j++) {
                    b[i][j] = a[i][j];
                }
            }
            memset(c, 0, sizeof(c));
            int cnt = 0;
            for (int i = 0; i < n; i++) {
                c[0][i] = (1 & (kase>>(n - i - 1)));
                if (c[0][i]) {
                    fff(0, i);
                    cnt++;
                }
            }
            for (int i = 1; i < m; i++) {
                for (int j = 0; j < n; j++) {
                    if (b[i - 1][j]) {
                        c[i][j] = 1;
                        fff(i, j);
                        cnt++;
                    }
                }
            }
            bool ok = true;
            for (int i = 0; i < n; i++) {
                if (b[m - 1][i]) {
                    ok = false;
                    break;
                }
            }
            if (ok && cnt < minf) {
                minf = cnt;
                for (int i = 0; i < m; i++) {
                    for (int j = 0; j < n; j++) {
                        ans[i][j] = c[i][j];
                    }
                }
            }
        }
        if (minf == 1000) {
            printf("IMPOSSIBLE\n");
        }
        else {
            for (int i = 0; i < m; i++) {
                printf("%d", ans[i][0]);
                for (int j = 1; j < n; j++) {
                    printf(" %d", ans[i][j]);
                }
                printf("\n");
            }
        }
    }
    return 0;
}