Leetcode 112 Path Sum.

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.

It is not a hard problem, but I spend a lot of time on it.

It is really confusing for me about the "return", my original code have two returns, then if I add a return for the whole system, every time the program execute to that line, it will return a false. Will not do the rest any more.

``````
/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean hasPathSum(TreeNode root, int sum) {
if(root==null ){
return false;
}

if(root.val==sum && root.left==null && root.right==null){
return true;
}
if(root!=null && root.left!=null){
root.left.val=(root.val+root.left.val);
}
if(root!=null && root.right!=null){
root.right.val=(root.val+root.right.val);
}

return hasPathSum(root.left,sum)||hasPathSum(root.right,sum);

}
}
``````