[LeetCode] Problem 112 - Path Sum

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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.

Note

A leaf is a node with no children.

Example

Given the below binary tree and sum = 22,

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2
3
4
5
6
7
      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.

Code

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public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}
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public boolean hasPathSum(TreeNode root, int sum) {
    if (root == null)
        return false;
    
    if (root.left == null && root.right == null)
        return sum == root.val;

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