Hdu 5423 Rikka with Tree (DFS)

problem Description

As we know, Rikka isPoor at math. Yuta isWorrying about ThisSituation, so he gives Rikka some math tasks to practice. There isOne of them:for a tree T, let F (t,i) be the distance between Vertice1and Vertice I. (the length of each edge is 1). Trees A and B are similiarifand onlyifThe same number of vertices and forEach I meet F (a,i) =F (b,i). Trees A and B are differentifand onlyifThey has different numbers of vertices or there exist an number I which vertice I had different fathersinchTree aand tree B when Vertice1  isRoot. Tree A isSpecialifand onlyifThere doesn't exist an tree B which A and B is different and A and B are similiar.Now he wants to knowifA tree isSpecial. It isToo difficult forRikka. Can you help her?

Input

 - testcases. For each testcase, the first line contains a number n (1≤n≤). Then n−1 lines follow. Each line contains the numbers u,v (1 is an edge between U and V.

Output

if  is " YES " " NO ".

Sample Input

3
1 2
2 3
4
1 2
2 3
1 4

Sample Output

YESNO

Hintfor the second testcase, this tree was similiar with the given tree:41 21 43 4

SourceBestcoder Round #53 (Div.2)

According to test instructions can be constructed out of the special tree has three cases (all with node 1 as the root), the first is a straight line, the second is a straight end of the flowering, the third is direct flowering. Then you can know for each depth of the points for 1,1,1,...,x,0,0, .... Then DFS can look it up again.

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <vector>5#include <Set>6#include <map>7#include <queue>8#include <algorithm>9 using namespacestd;Ten #defineN 1006 Onevector<int>G[n]; Avector<int>Deep[n]; - intVis[n]; - voidDfsintStintd) { thevis[st]=1; - Deep[d].push_back (ST); -      for(intI=0; I<g[st].size (); i++){ -         intu=G[st][i]; +         if(!Vis[u]) { -DFS (u,d+1); +         } A     } at } - intMain () - { -     intN; -      while(SCANF ("%d", &n) = =1){ -  in          for(intI=0; i<=n;i++) { - g[i].clear (); to deep[i].clear (); +         } -memset (Vis,0,sizeof(Vis)); the  *          for(intI=1; i<n;i++){ $             intu,v;Panax Notoginsengscanf"%d%d",&u,&v); - G[u].push_back (v); the g[v].push_back (u); +         } ADfs1,0); the  +  -         intt=0; $          while(deep[t].size () = =1) t++; $  -         intnum=deep[t].size (); -         if(num+t!=N) { theprintf"no\n"); -}Else{Wuyiprintf"yes\n"); the         } -          Wu     } -     return 0; About}

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Hdu 5423 Rikka with Tree (DFS)