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/**

* 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 a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public class PathSum112 {

public boolean hasPathSum(TreeNode root, int sum) {

return sum(root, sum, 0);

}

private boolean sum(TreeNode root, int sum, int sumForNow) {

if (root == null) {

return false;

}

sumForNow += root.val;

if (sumForNow == sum && root.left == null && root.right == null) {

return true;

}

if (sum(root.left, sum, sumForNow)) {

return true;

}

return sum(root.right, sum, sumForNow);

}

/**

* https://discuss.leetcode.com/topic/3149/accepted-my-recursive-solution-in-java

*/

public boolean hasPathSum2(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);

}

}