题目描述
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.
Note: A leaf is a node with no children.
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.
思路与实现
class Solution {
public boolean hasPathSum(TreeNode root, int sum) {
if (root == null) {
return false;
}
return dfs(root, sum);
}
private boolean dfs(TreeNode node, int sum) {
if (node == null) {
return false;
}
if (node.val == sum && node.left == null && node.right == null) {
return true;
}
return dfs(node.left, sum - node.val) || dfs(node.right, sum - node.val);
}
}
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