CodeForces 780C Andryusha and Colored BalloonsDFS

Posted 2022-11-23

题目链接：​​http://codeforces.com/problemset/problem/780/C​​​
题意：给你一棵树，让你用最少的颜色给这棵树染色，相邻节点的颜色不同
解析：DFS染色

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <iostream>
#include <vector>
#include <queue>
#include <set>
using namespace std;
const int maxn = 1e6+100;
vector<int>G[maxn];
int vis[maxn];
void dfs(int now,int last)

    int cnt = 1;
    for(int i=0;i<G[now].size();i++)
    
        if(G[now][i]!=last)
        
            while(cnt==vis[now]||cnt==vis[last])
                cnt++;
            vis[G[now][i]] = cnt++;
        
    
    for(int i=0;i<G[now].size();i++)
    
        if(G[now][i]!=last)
            dfs(G[now][i],now);
    

int main()

    int n;
    scanf("%d",&n);
    for(int i=0;i<=n;i++)
        G[i].clear();
    for(int i=0;i<n-1;i++)
    
        int x,y;
        scanf("%d %d",&x,&y);
        G[y].push_back(x);
        G[x].push_back(y);
    
    memset(vis,0,sizeof(vis));
    vis[1] = 1;
    dfs(1,0);
    int ans = 0;
    for(int i=1;i<=n;i++)
        ans = max(ans,vis[i]);
    printf("%d\\n",ans);
    for(int i=1;i<=n;i++)
    
        if(i)printf(" ");
        printf("%d",vis[i]);
    
    puts("");
    return 0;