Solution.java

package Tree.easy.No_112_Path_Sum;

import Tree.TreeNode;

/**
 * FileName: Solution
 * Author:   EdisonLi的家用MacBook Pro
 * Date:     2019-03-29 14:45
 * Description: Path Sum
 * <p>
 * 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.
 * <p>
 * Note: A leaf is a node with no children.
 * <p>
 * Example:
 * <p>
 * Given the below binary tree and sum = 22,
 * <p>
 *       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 class Solution {
    public boolean hasPathSum(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);
    }
}