Even Tree

Link:

　　https://www.hackerrank.com/challenges/even-tree

 def search(a,b): # 根据核心算法和题目要求要筛选边
     seen = {}
     seen[a] = True
     q = []

     for x in adj[a]:
         if x != b:
             seen[x] = True
             q.append(x)
     s = len(q) + 1
     while q:
         n = q.pop()
         for x in adj[n]:
             if x not in seen:
                 seen[x] = True
                 q.append(x)
                 s += 1
     return (s+1)%2

 [N,M] = [int(x) for x in raw_input().split(' ')]
 edges = [] # 保存边的list
 adj = {} # 保存邻接的dict
 for a in xrange(1,N+1): # 初始化
     adj[a] = []

 for a in xrange(M):
     [x,y] = [int(z) for z in raw_input().split(' ')]
     adj[x].append(y) # 保存边的对应，没有方向性
     adj[y].append(x)
     edges.append((x,y)) # 保存边边

 count = 0
 for e in edges:
     (x,y) = e
     if search(x,y): #依次查看每个边是否能移开
         count += 1
         adj[x].remove(y)
         adj[y].remove(x)

 print count

学习

　　图的基本结构

　　　　edge, adj建立dict/list保存

　　然后根据算法进行计算

　　本质

　　　　换了一个数据的结构