Leetcode 437. Path Sum III

文章作者：Tyan
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1. Description

2. Solution

• Recursive

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int pathSum(TreeNode* root, int sum) {
        if(!root) {
            return 0;
        }
        int paths = 0;
        path(root, sum, paths);
        return paths + pathSum(root->left, sum) + pathSum(root->right, sum);
    }
    
    void path(TreeNode* root, int sum, int& paths) {
        if(root->val == sum) {
            paths++;
        }
        if(root->left) {
            path(root->left, sum - root->val, paths);
        }
        if(root->right) {
            path(root->right, sum - root->val, paths);
        }
    }
};

Reference

1. https://leetcode.com/problems/path-sum-iii/description/