深度优先、广度优先

'''
        1
       / \
      2   3
     / \
    4   5 
'''

class TreeNode:
    def __init__(self,val):
        self.val = val
        self.left = None
        self.right = None


# 深度优先-先序遍历
def dfs_pre(node):
    if not node:
        return    
    print(node.val) 
    dfs_pre(node.left)
    dfs_pre(node.right)

    
# 深度优先-中序遍历
def dfs_mid(node):
    if not node:
        return    
    dfs_mid(node.left)
    print(node.val) 
    dfs_mid(node.right)

# 深度优先-后序遍历
def dfs_dec(node):
    if not node:
        return    
    dfs_dec(node.left)
    dfs_dec(node.right)
    print(node.val) 

# 广度优先,列表版
def bfs(node):
    q = [(node,0)]
    while q:
        node,level = q.pop(0)
        if node is None:
            continue
        print(node.val)
        q.append((node.left,level+1))
        q.append((node.right,level+1))

from collections import deque     
# 广度优先,双端队列版
def bfs(node):
    q = deque([(node,0)])
    while q:
        node,level = q.popleft()
        if node is None:
            continue
        print(node.val)
        q.append((node.left,level+1))
        q.append((node.right,level+1))


def main():
    root = TreeNode(1)
    n1 = TreeNode(2)
    n2 = TreeNode(3)
    n3 = TreeNode(4)
    n4 = TreeNode(5)
    root.left = n1
    root.right = n2
    n1.left = n3
    n1.right = n4
    
    print("深度优先-先序遍历".center(20,"="))
    dfs_pre(root)
    print("深度优先-中序遍历".center(20,"="))
    dfs_mid(root)
    print("深度优先-后序遍历".center(20,"="))
    dfs_dec(root)
    print("广度优先".center(20,"="))
    bfs(root)


if __name__ == "__main__":
    main()

标签：node,优先,right,val,dfs,深度,print,广度,left
来源： https://www.cnblogs.com/ray-mmss/p/16626047.html