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LeetCode: Path Sum 解题报告
Path Sum
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.
SOLUTION 1:
相当简单的题目,用递归解决。base case: 如果root是叶子,并且sum为root的值,返回true.
否则在左右分别 找一下就好(调用递归),任何一边返回true都可以的。
https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/tree/hasPathSum.java
1 public boolean hasPathSum(TreeNode root, int sum) { 2 if (root == null) { 3 return false; 4 } 5 6 if (root.left == null && root.right == null && sum == root.val) { 7 return true; 8 } 9 10 return hasPathSum(root.left, sum - root.val)11 || hasPathSum(root.right, sum - root.val);12 }
LeetCode: Path Sum 解题报告
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