题解

造福后代

#include <iostream>
using namespace std;
int ans = 10;
bool g[5][5],vis[5][5];
void turn(int x, int y) {
	g[x][y] = !g[x][y];
	g[x - 1][y] = !g[x - 1][y];
	g[x + 1][y] = !g[x + 1][y];
	g[x][y + 1] = !g[x][y + 1];
	g[x][y - 1] = !g[x][y - 1];
}
void dfs(int n) {
	if (n > ans) return ;
	int sum = 0;
	for (int i = 1; i <= 3; i++)
		for (int j = 1; j <= 3; j++)
			sum += g[i][j];
	if (sum == 9) ans = min(ans, n - 1);
	for (int i = 1; i <= 3; i++)
		for (int j = 1; j <= 3; j++) {
			if (!vis[i][j]) {
				vis[i][j] = 1;
				turn(i, j);
				dfs(n + 1);
				vis[i][j] = 0;
				turn(i, j);
			}
		}
}
int main() {
	for (int i = 1; i <= 3; i++) for (int j = 1; j <= 3; j++) cin >> g[i][j];
	dfs(1);
	cout << ans << endl;
	return 0;
}