【贪心】【DFS】Codeforces Round #403 (Div. 2, based on Technocup 2017 Finals) C. Andryusha and Colored Balloons

从任意点出发，贪心染色即可。

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

#include<cstdio> #include<algorithm> using namespace std; int v[200010<<1],next[200010<<1],first[200010],e; void AddEdge(int U,int V) {     v[++e]=V;     next[e]=first[U];     first[U]=e; } bool vis[200010]; int n,col[200010]; void dfs(int U,int n1,int n2) {     vis[U]=1;     int co=0;     for(int i=first[U];i;i=next[i])       if(!vis[v[i]])         {           ++co;           while(co==n1 || co==n2)             ++co;           col[v[i]]=co;           dfs(v[i],col[U],col[v[i]]);         } } int main() { //  freopen("c.in","r",stdin);     int x,y;     scanf("%d",&n);     for(int i=1;i<n;++i)       {         scanf("%d%d",&x,&y);         AddEdge(x,y);         AddEdge(y,x);       }     col[1]=1;     dfs(1,1,-1);     printf("%d\n",*max_element(col+1,col+n+1));     for(int i=1;i<n;++i)       printf("%d ",col[i]);     printf("%d\n",col[n]);     return 0; }