lc112. Path Sum

112. Path Sum Easy

947

309

Favorite

Share Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

Note: A leaf is a node with no children.

Example:

Given the below binary tree and sum = 22,

  5
 / \
4   8
复制代码

/ /
11 13 4 / \
7 2 1 return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

思路：深度优先算法，递减，只要中途target==0，且无左右子树，即有

代码：python3

class Solution:
    def hasPathSum(self, root: TreeNode, sum: int) -> bool:
        cache=[False]
        def dfs(root,target):
            if not root:return
            target = target-root.val
            if target==0 and not root.left and not root.right:
                cache[0]=True
            dfs(root.left,target)
            dfs(root.right,target)
        dfs(root,sum)
        return cache[0]
复制代码

转载于:https://juejin.im/post/5d01ec5f518825276a2865f7