标签：而不是 修改 tom blog car 遍历 res ... logs
#1
# here is a list of edges: T = [(‘Bob‘,‘Eve‘),(‘Alice‘,‘Carol‘),(‘Eve‘,‘Frank‘),(‘Alice‘,‘Doug‘),(‘Frank‘,‘Ginger‘), (‘Eve‘,‘Howard‘),(‘Carol‘,‘Irene‘),(‘Frank‘,‘Jeff‘),(‘Doug‘,‘Kathy‘),(‘Bob‘,‘Luis‘), (‘Alice‘,‘Bob‘),(‘Bob‘,‘Mabel‘),(‘Ginger‘,‘Norm‘),(‘Howard‘,‘Oprah‘),(‘Carol‘,‘Peter‘), (‘Kathy‘,‘Queen‘),(‘Mabel‘,‘Ursala‘),(‘Luis‘,‘Ronald‘),(‘Ginger‘,‘Sarah‘),(‘Irene‘,‘Tom‘), (‘Jeff‘,‘Vince‘),(‘Peter‘,‘Wanda‘),(‘Oprah‘,‘Xanthia‘),(‘Norm‘,‘Yaakov‘),(‘Luis‘,‘Zandra‘)] print (‘T has‘,len(T),‘edges‘) vertices = set() for edge in T: s,t = edge vertices.add(s) vertices.add(t) print (‘T has‘,len(vertices),‘vertices‘)
#2
So this could be a tree. Now lets compute the number of parents for each vertex. The result confirms that we indeed have a tree and that the root is Alice (right?).
np = {} for v in vertices: np[v] = 0 for parent,child in T: np[child] += 1 print (np)
Yes.
We now construct a dictionary of pairs (p,c) where p is the parent of the list of children c
#3
adjacency_map = {} for v in vertices: adjacency_map[v] = [] for p,c in T: adjacency_map[p].append(c) print ("node and children:") for p in adjacency_map: print (p, ":", adjacency_map[p]) print () print (adjacency_map)
print (5*"Hello!")
#4
做DFS,相当于树的前序遍历,python写起来相当简洁.DFS是遇到深度更深的节点立马去执行, 而不是像BFS一样拖着,加入队列,直到无法同层遍历时才选择深入(层序遍历).
# A recursive Depth-First traversal of a tree defined by an adjacency_map def print_tree_depth_first(parent, adjacency_map, level=0): print (level*‘ ‘, parent) children = adjacency_map[parent] for child in children: print_tree_depth_first(child, adjacency_map, level+1) root = ‘Alice‘ print_tree_depth_first(root, adjacency_map)
BFS
from collections import deque # breadth-first traversal using a queue def print_tree_breath_first(root, adjacency_map): Q = deque() Q.append(root) while len(Q)>0: p = Q.popleft() print (p) children = adjacency_map[p] for child in children: Q.append(child) print_tree_breath_first("Alice", adjacency_map)
修改成如下打印格式:
1: Alice
2: Carol Doug Bob
3: ...
标签：而不是 修改 tom blog car 遍历 res ... logs
原文地址：http://www.cnblogs.com/kprac/p/7747243.html
