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## 呃，我是多蠢，没有IMPOSSIBLE就提交了

Posted by youshiki at 2016-08-26 16:30:14 on Problem 3279
```#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iomanip>
#include<iostream>
#include<algorithm>
using namespace std;

/* POJ 3279 */

const int N = 20;
const int INF = 1e9 + 7;

bool G[N][N];
bool T[N][N];
int n, m, ans = INF, pre;

const int mv[5][2] = {
0,0,1,0,0,1,-1,0,0,-1
};

inline void putMatrix(void) {

puts(""); puts("/////Matrix/////");
for (int i = 1; i <= n; i++, puts(""))
for (int j = 1; j <= m; j++)
printf("%d ", T[i][j]);

}

inline void change(int x, int y) {

for (int i = 0; i < 5; i++)
T[x + mv[i][0]][y + mv[i][1]] ^= 1;

}

inline bool check(void) {

for (int i = 1; i <= m; i++)
if (T[n][i])return false;

return true;

}

inline int solve(int p) {

memcpy(T, G, sizeof(T));

int res = 0;

for (int i = 0; i < m; i++)
if ((p >> i) & 1)res++, change(1, i + 1);

for (int i = 1; i < n; i++)
for (int j = 1; j <= m; j++)
if (T[i][j])res++, change(i + 1, j);

//putMatrix();

return check() ? res : INF;

}

memcpy(T, G, sizeof(T));

for (int i = 0; i < m; i++) {
printf("%d ", (p >> i) & 1);
if ((p >> i) & 1)change(1, i + 1);
}puts("");

for (int i = 1; i < n; i++, puts(""))
for (int j = 1; j <= m; j++) {
printf("%d ", T[i][j]);
if (T[i][j])change(i + 1, j);
}

}

signed main(void) {

scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
scanf("%d", &G[i][j]);

for (int i = 0, tmp; i < (1 << m); i++)
if (ans > (tmp = solve(i)))ans = tmp, pre = i;

else puts("IMPOSSIBLE");

#ifndef ONLINE_JUDGE
system("pause");
#endif // !ONLINE_JUDGE

}```

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