112. Path Sum
Question
Total Accepted: 91133 Total
Submissions: 295432 Difficulty: Easy
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.
For 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.
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显然深搜求解,简单高效。注意叶子节点的定义,当且仅当左右孩子都为空时,才是叶子节点。如果一个节点有一个孩子时,是不能作为leaf的。
我的AC代码
public class PathSum { static Boolean ok = false; /** * @param args */ public static void main(String[] args) { TreeNode treeNode = new TreeNode(1); TreeNode t1 = new TreeNode(2); System.out.println(hasPathSum(treeNode, 1)); System.out.println(hasPathSum(null, 0)); treeNode.left = t1; System.out.println(hasPathSum(treeNode, 1)); } public static boolean hasPathSum(TreeNode root, int sum) { if(root == null) return false; ok = false; dfs(root, sum, 0); return ok; } public static void dfs(TreeNode root, int sum, int s) { if(ok == true) return; if(root.left == null && root.right == null) { if (s + root.val == sum) { ok = true; } return; } if(root.left != null) dfs(root.left, sum, s + root.val); if(root.right != null) dfs(root.right, sum, s + root.val); } }
时间: 2024-10-13 12:02:54