版权声明：https://blog.csdn.net/qq_41730082 https://blog.csdn.net/qq_41730082/article/details/85234911
题目链接
我们枚举第一列的答案，然后我们以此为基础向下搜索，题目要我们找的是‘1’数最少并且在‘1’数相等的时候，字典序最小的答案，直接按顺序枚举即可。
给几组测试样例，过了这几组，就是基本过了，一道构造题，卡了为好几个小时……
#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
#define INF 0x3f3f3f3f
#define son1 (j-1)>0? ans[i-1][j-1] : 0
#define son2 (j+1)<=M? ans[i-1][j+1] : 0
#define son3 (i-2)>0? ans[i-2][j] : 0
#define copppy(pr, ans) memcpy(pr, ans, sizeof(ans))
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int maxN = 18;
int N, M, mp[maxN][maxN], ans[maxN][maxN], cnt, pr[maxN][maxN], now;
bool check()
{
now = 0;
for(int i=1; i<=M; i++) if(ans[1][i]) now++;
for(int i=2; i<=N; i++)
{
for(int j=1; j<=M; j++)
{
int s1 = son1, s2 = son2, s3 = son3;
int tmp = mp[i-1][j] + s1 + ans[i-1][j] + s2 + s3;
if( tmp & 1 ) { ans[i][j] = 1; now++; }
else ans[i][j] = 0;
}
}
for(int i=1; i<=M; i++) if( (ans[N-1][i] + mp[N][i] + ans[N][i-1] + ans[N][i+1] + ans[N][i]) & 1) return false;
return true;
}
bool dfs_first_line(int y, int val)
{
ans[1][y] = val;
if(y == M)
{
bool flag = check();
if(flag && cnt>now)
{
cnt = now;
copppy(pr, ans);
}
return flag;
}
bool flag = dfs_first_line(y+1, 0);
if(!flag) flag = dfs_first_line(y+1, 1);
else dfs_first_line(y+1, 1);
return flag;
}
int main()
{
while(scanf("%d%d", &N, &M)!=EOF)
{
memset(ans, 0, sizeof(ans));
memset(pr, 0, sizeof(pr));
for(int i=1; i<=N; i++) for(int j=1; j<=M; j++) scanf("%d", &mp[i][j]);
bool flag = false;
cnt = INF;
flag = dfs_first_line(1, 0);
if(!flag) flag = dfs_first_line(1, 1);
else dfs_first_line(1, 1);
if(flag)
{
for(int i=1; i<=N; i++)
{
for(int j=1; j<=M; j++)
{
printf("%d%c", pr[i][j], j==M?'\n':' ');
}
}
}
else printf("IMPOSSIBLE\n");
}
return 0;
}
/*
2 3
1 1 0
1 0 0
ans:
1 0 0
0 0 0
/////
2 2
1 1
1 1
ans:
1 1
1 1
/////
5 3
1 1 0
1 0 1
1 0 0
0 1 1
1 1 1
ans:
0 0 0
1 1 0
1 0 0
1 0 0
0 0 1
mine:
1 0 0
0 0 0
0 0 1
1 1 1
0 0 0
*/