leetcode 112. Path sum recursion

topic description

Path sum: link to original title

Ideas

It can be solved recursively

• Encountered empty node: Since the tree is empty, there is no path from the root node to the leaf node, return false
• Currently leaf node: determine whether the sum of the current path is equal to targetSum
• Currently a general node: Recursively go to the left subtree and right subtree, and subtract the value of the current node from the target value

Code

class Solution {public:bool hasPathSum(TreeNode* root, int targetSum) {if(!root) return false; //Because the tree is empty, there is no path from the root node to the leaf node, and the boundary point is reachedif(!root->left&&!root->right) return targetSum==root->val; //To the leaf node, judge whether it meets the conditionsreturn hasPathSum(root->left,targetSum-root->val)||hasPathSum(root->right,targetSum-root->val); //The leaf node is not reached, recurse downward}};