Path Sum

Posted 2020-06-23 YuriFLAG

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.

 1 public class Solution {
 2     public boolean hasPathSum(TreeNode root, int sum) {
 3         if (root == null) {
 4             return false;
 5         }
 6         if (root.left == null && root.right == null) {
 7             return sum == root.val;
 8         }
 9         return hasPathSum (root.left, sum - root.val)
10             || hasPathSum(root.right, sum - root.val);
11     }
12 }