小黑leetcode清爽雨天之旅，刚吃完宇飞牛肉面、麻辣烫和啤酒:112. 路径总和

小黑自己的解法

# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
        self.flag = False
        if not root:
            return self.flag
        def list_path(root,sum_):
            sum_ = root.val + sum_
            # 判断是否到达叶子结点
            if (not root.left) and (not root.right):
                #print(sum_)
                if sum_ == targetSum:
                    self.flag = True
            if root.left and not self.flag :
                list_path(root.left,sum_)
            if root.right and not self.flag:
                list_path(root.right,sum_)
        list_path(root,0)
        return self.flag

递归法

# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
        if not root:
            return False
        
        if  (not root.left and not root.right):
            return targetSum == root.val

        return self.hasPathSum(root.left,targetSum - root.val) or self.hasPathSum(root.right,targetSum - root.val)

广度优先搜索

# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
        if not root:
            return False
        q_node = deque([root])
        q_num = deque([root.val])
        # 队列操作
        while q_node:
            node = q_node.popleft()
            num = q_num.popleft()
            # node为叶子结点
            if (not node.left) and (not node.right):
                if num == targetSum:
                    return True
                continue
            if node.left:
                q_node.append(node.left)
                q_num.append(num + node.left.val)
            if node.right:
                q_node.append(node.right)
                q_num.append(num + node.right.val)
        return False