112. Path Sum

二刷 06/2022

Runtime: 0 ms, faster than 100.00% of Java online submissions for Path Sum.

Memory Usage: 44.3 MB, less than 12.60% of Java online submissions for Path Sum.

/**

 * Definition for a binary tree node.

 * public class TreeNode {

 *     int val;

 *     TreeNode left;

 *     TreeNode right;

 *     TreeNode() {}

 *     TreeNode(int val) { this.val = val; }

 *     TreeNode(int val, TreeNode left, TreeNode right) {

 *         this.val = val;

 *         this.left = left;

 *         this.right = right;

 *     }

 * }

 */

class Solution {

    public boolean hasPathSum(TreeNode root, int targetSum) {

        if (root == null) {

            return false;

        }

        targetSum -= root.val;

        if (root.left == null && root.right == null) {

            return targetSum == 0;

        }

        return hasPathSum(root.left, targetSum) || hasPathSum(root.right, targetSum);

    }

}

一刷

唉又犯这个错误了
每次特指是leaf的时候都不能用root == null作为终止条件
而应该用root.left == null && root.right == null作为终止条件
13.08 %

public class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        if (root == null) return false;
        //leaf node
        if (root.left == null && root.right == null && root.val == sum) return true;
        return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
    }
}