[LeetCode] 112. Path Sum
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.
For example:Given the below binary tree and
sum = 22
,5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1
return true, as there exist a root-to-leaf path
5->4->11->2
which sum is 22.
Thought process:
Traverse all root-to-leaf paths.
Solution:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public boolean hasPathSum(TreeNode root, int sum) { if (root == null) { return false; } if (root.left == null && root.right == null && sum - root.val == 0) { return true; } return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val); } } |
Time complexity: O(2^h) where h = height of the tree.
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