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.

Note: A leaf is a node with no children.

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 target) {
    if(root == null) return false;
    if(target == root.val && root.left == null && root.right == null) return true;
    return hasPathSum(root.left, target-root.val) || hasPathSum(root.right, target-root.val);
}