题目
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.
代码
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
boolean flag=false;
public boolean hasPathSum(TreeNode root, int sum) {
if(root==null) return flag;
isTrue(root,sum);
return flag;
}
public void isTrue(TreeNode root, int sum){
if(root==null) return;
if(root.right==null && root.left==null && sum-root.val==0) flag=true;
else {
isTrue(root.left,sum-root.val);
isTrue(root.right,sum-root.val);
}
}
}
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