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.
/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public boolean hasPathSum(TreeNode root, int sum) { return pathSum(root,sum,0); } public boolean pathSum(TreeNode node,int sum,int path){ if(node==null) return false; if((node.val+path)==sum && node.left==null && node.right==null) return true; else return pathSum(node.left,sum,node.val+path)||pathSum(node.right,sum,node.val+path); } }思路:递归。注意。题目要求,结尾的必须是叶子节点。