[LeetCode] Path Sum
LeetCode path sum
2023-09-11 14:17:25 时间
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.
Tree Depth-first Search
AC code如下,但是我不理解为什么 root==NULL && sum==0 时要返回false??
考虑中间节点,只有一个左子树,右子树为NULL,所以只能到左子树继续判断了。。所以为NULL时要返回false吧,我想
class Solution { public: bool hasPathSum(TreeNode *root, int sum) { if(root == NULL) { return false; } if(root->left == NULL && root->right == NULL) //判断叶节点 { if(root->val == sum) return true; return false; } if ( hasPathSum(root->left, sum - root->val) // 递归 || hasPathSum(root->right, sum - root->val) ) return true; return false; } };
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