782C. Andryusha and Colored Balloons DFS

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题意: 给出一棵树,要求为其染色,并且使任意节点都不与距离2以下的节点颜色相同

 

思路: 直接DFS。由某节点出发的DFS序列,对于其个儿子的cnt数+1,那么因为DFS遍历的性质可保证兄弟结点的颜色不同,只需考虑当前节点是否与父亲结点和父亲的父亲结点颜色是否相同。

/** @Date    : 2017-05-09 22:37:25
  * @FileName: 782C DFS.cpp
  * @Platform: Windows
  * @Author  : Lweleth (SoundEarlf@gmail.com)
  * @Link    : https://github.com/Lweleth
  * @Version : $Id$
  */
#include <bits/stdc++.h>
#define LL long long
#define PII pair
#define MP(x, y) make_pair((x),(y))
#define fi first
#define se second
#define PB(x) push_back((x))
#define MMG(x) memset((x), -1,sizeof(x))
#define MMF(x) memset((x),0,sizeof(x))
#define MMI(x) memset((x), INF, sizeof(x))
using namespace std;

const int INF = 0x3f3f3f3f;
const int N = 1e5+20;
const double eps = 1e-8;

vectorvt[2*N];
int ans[2*N];
int n, ma;

int dfs(int x, int pre)
{
	int l = vt[x].size();
	int c = 0;
	for(int i = 0; i < l; i++)
	{
		int nw = vt[x][i];
		if(ans[nw] || nw == pre)
			continue;
		c++;
		while(c == ans[pre] || c == ans[x])
			c++;
		ans[nw] = c; 
		ma = max(c, ma);
		dfs(nw, x);
	}
}

int main()
{
	while(cin >> n)
	{
		MMF(ans);
		for(int i = 0; i <= n; i++) vt[i].clear();
		for(int i = 0; i < n - 1; i++)
		{
			int x, y;
			scanf("%d%d", &x, &y);
			vt[x].PB(y);
			vt[y].PB(x);
		}
		ma = 0;
		ans[1] = 1;
		dfs(1, 1);
		printf("%d\n", ma);
		for(int i = 1; i <= n; i++)
			printf("%d%s", ans[i], i==n?"\n":" ");
	}	
    return 0;
}