CODE 21: 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) {// Start typing your Java solution below// DO NOT write main() functionif (null == root) {return false;}return dfs(root, 0, sum);}private boolean dfs(TreeNode root, int current, int sum) {if (root.left == null && root.right == null) {if (current + root.val == sum) {return true;} else {return false;}}boolean is = false;if (root.left != null) {is = dfs(root.left, current + root.val, sum);}if (is) {return is;}if (root.right != null) {is = dfs(root.right, current + root.val, sum);}return is;}