[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.

public boolean hasPathSum(TreeNode root, int sum) { if (root == null) return false; //这个判断包含了叶子节点的含义在里面 if (root.left == null && root.right == null) return sum == root.val; return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val); }

思来想去还是递归最为简便。其他的非递归我也想不出来。