P1985 [USACO07OPEN]翻转棋

题目链接：

翻转棋

题目分析：

先状压/(dfs)枚举第一排状态，然后在每个(1)下面翻，即确定了第一排就确定了后面的状态
最后验证一下最后一排是不是全0即可

代码：

#include<bits/stdc++.h> 
#define N 50
using namespace std;
inline int read() {
	int cnt = 0, f = 1; char c = getchar();
	while (!isdigit(c)) {if (c == '-') f = -f; c = getchar();}
	while (isdigit(c)) {cnt = (cnt << 3) + (cnt << 1) + (c ^ 48); c = getchar();}
	return cnt * f;
}
int mapp[N][N], m, n, cnt, ans[N][N], res = (1 << 30);
bool vis[N][N], flag;
void rev(int x, int y) {
	mapp[x][y] ^= 1;
	mapp[x][y - 1] ^= 1;
	mapp[x - 1][y] ^= 1;
	mapp[x][y + 1] ^= 1;
	mapp[x + 1][y] ^= 1; 
}
void cpy() {
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) ans[i][j] = vis[i][j];
}
void work() {
	for (register int i = 2; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (mapp[i - 1][j]) rev(i, j), vis[i][j] = 1, ++cnt;
	flag = 0;
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (mapp[i][j]) flag = 1;
	if (!flag) if (cnt < res) cpy(), res = cnt;

	for (register int i = 2; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (vis[i][j]) rev(i, j), vis[i][j] = 0, --cnt; 
}
void dfs_(int k) {
	if (!k) {work(); return;}
	dfs_(k - 1), rev(1, k), vis[1][k] = 1, ++cnt;
	dfs_(k - 1), rev(1, k), vis[1][k] = 0, --cnt;
}
int main() {
	m = read(), n = read();
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) mapp[i][j] = read();
	dfs_(n); 
	if (res == (1 << 30)) return printf("IMPOSSIBLE"), 0; 
	for (register int i = 1; i <= m; ++i) {
		for (register int j = 1; j <= n; ++j) printf("%d ", ans[i][j]);
		printf("
");
	}
	return 0;
}#include<bits/stdc++.h> 
#define N 50
using namespace std;
inline int read() {
	int cnt = 0, f = 1; char c = getchar();
	while (!isdigit(c)) {if (c == '-') f = -f; c = getchar();}
	while (isdigit(c)) {cnt = (cnt << 3) + (cnt << 1) + (c ^ 48); c = getchar();}
	return cnt * f;
}
int mapp[N][N], m, n, cnt, ans[N][N], res = (1 << 30);
bool vis[N][N], flag;
void rev(int x, int y) {
	mapp[x][y] ^= 1;
	mapp[x][y - 1] ^= 1;
	mapp[x - 1][y] ^= 1;
	mapp[x][y + 1] ^= 1;
	mapp[x + 1][y] ^= 1; 
}
void cpy() {
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) ans[i][j] = vis[i][j];
}
void work() {
	for (register int i = 2; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (mapp[i - 1][j]) rev(i, j), vis[i][j] = 1, ++cnt;
	flag = 0;
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (mapp[i][j]) flag = 1;
	if (!flag) if (cnt < res) cpy(), res = cnt;

	for (register int i = 2; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) if (vis[i][j]) rev(i, j), vis[i][j] = 0, --cnt; 
}
void dfs_(int k) {
	if (!k) {work(); return;}
	dfs_(k - 1), rev(1, k), vis[1][k] = 1, ++cnt;
	dfs_(k - 1), rev(1, k), vis[1][k] = 0, --cnt;
}
int main() {
	m = read(), n = read();
	for (register int i = 1; i <= m; ++i)
		for (register int j = 1; j <= n; ++j) mapp[i][j] = read();
	dfs_(n); 
	if (res == (1 << 30)) return printf("IMPOSSIBLE"), 0; 
	for (register int i = 1; i <= m; ++i) {
		for (register int j = 1; j <= n; ++j) printf("%d ", ans[i][j]);
		printf("
");
	}
	return 0;
}