AcWing 2060. 奶牛选美（DFS）

Posted 2022-02-11 MangataTS

题目链接

https://www.acwing.com/problem/content/2062/

思路

先DFS染色，将这两部分分开，分别用1和2标记，然后对于第一堆的每个元素直接用BFS跑一个最短路即可

代码

#include<bits/stdc++.h>
using namespace std;
#define endl "\\n"

const int N = 100;

char mp[N][N];
int a[N][N];
int n,m;

int dx[4]=-1,1,0,0;
int dy[4]=0,0,-1,1;

bool vis[N][N];

bool check(int x,int y) 
	if(x >= 1 && x <= n && y >= 1 && y <= m) return true;
	return false;


void dfs(int x,int y,int k) 
	if(vis[x][y] || mp[x][y] != 'X') return;
	vis[x][y] = true;
	mp[x][y] = '.';
	a[x][y] = k;
	for(int i = 0;i < 4; ++i) 
		int nx = x + dx[i];
		int ny = y + dy[i];
		if(check(nx,ny))
			dfs(nx,ny,k);
	


int ans = 0x3f3f3f3f;

struct Node 
	int x,y,step;
;



int bfs(int x,int y) 
	queue<Node> que;
	que.push(x,y,0);
	while(!que.empty()) 
		Node p = que.front();
		que.pop();
		if(vis[p.x][p.y]) continue;
		vis[p.x][p.y] = true;
		if(a[p.x][p.y] == 2) 
			return p.step;
		
		for(int i = 0;i < 4; ++i) 
			int nx = p.x + dx[i];
			int ny = p.y + dy[i];
			if(check(nx,ny) && a[nx][ny] != 1) 
				que.push(nx,ny,p.step+1);
			
		
	
	return 0x3f3f3f3f;


int main()

	cin>>n>>m;
	for(int i = 1;i <= n; ++i) 
		for(int j = 1;j <= m; ++j) 
			cin>>mp[i][j];
		
	
	int k = 1;
	for(int i = 1;i <= n; ++i) 
		for(int j = 1;j <= m; ++j) 
			if(mp[i][j] == 'X') 
				dfs(i,j,k);
				k++;
			
		
	
//	puts("------------line begin--------------");
//	for(int i = 1;i <= n; ++i) 
//		for(int j = 1;j <= m; ++j) 
//			cout<<a[i][j]<<" \\n"[j==m];
//		
//	
//	puts("------------line end--------------");
	int ans = 0x3f3f3f3f;
	memset(vis,0,sizeof vis);
	for(int i = 1;i <= n; ++i) 
		for(int j = 1;j <= m; ++j) 
			if(a[i][j] == 1) 
				k = bfs(i,j);
				ans = min(ans,k);
				memset(vis,0,sizeof vis);
			
		
	
	cout<<ans-1<<endl;
	
	return 0;


/*

14 35
...................................
..................................X
..................................X
..................................X
................................X.X
................................XXX
...........X.X..................XXX
.......XXXXXXX.................XXXX
........XXXXXX..............XXX.XXX
........XXXXX...............XXXXX.X
......XXXXXXXX............X.XXXXXXX
....XXXXXXXXXX............XX.XXXXXX
...XXXXXXXXXXXXXX.........XXXXXXXXX
...XXXXXXXX.X..X.........XXXXXXXXXX
*/