[吐槽] Path Sum

Problem:

Write a function that given a tree, returns true if at least 2 paths down the tree have the same sum. A path is a series of nodes from the root to the leaf. （题做出来还不给第二轮的某P家的电面题，不过解法确实不太好的感觉）

// ex1:
//     2
//   / \
//   4   5
//  / 
// 1
// returns true // 2+4+1 = 2+5
// ex2:
//     3
//   /
//   4
//  / \
// 1   1
// returns true //3+4+1 = 3+4+1
// ex3:
//   1
//  / \
// 3   4
// returns false // 1+3 != 1+4

Java Code:

public class PathSum {
    class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;
        public TreeNode(int value) {
            this.val = value;
        }
    }

    public static boolean pathSum(TreeNode root) {
        if (root == null) {
            return false;
        }
        if (root.left != null && root.right != null) {
            boolean result = false;
            int left = pathSumValue(root.left);
            int right = pathSumValue(root.right);
            result = pathSum(root.left) || pathSum(root.right) || (left == right);
            return result;
        }
        if (root.left != null) {
            return pathSum(root.left);
        }
        return pathSum(root.right);
    }
    
    public static int pathSumValue(TreeNode root) {
        if (root.left == null && root.right == null) {
            return root.val;
        }
        if (root.left == null) {
            return pathSumValue(root.right) + root.val;
        }
        if (root.right == null) {
            return pathSumValue(root.left) + root.val;
        }
        return pathSumValue(root.left) + pathSumValue(root.right);
    }
    
    public static void main(String[] args) {
        TreeNode root = new TreeNode(2);
        root.left = new TreeNode(4);
        root.right = new TreeNode(5);
        root.left.left = new TreeNode(1);
        root.left.right = new TreeNode(1);
        System.out.println(pathSum(root));
    }
}