Path Sum II （C++）

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        vector<int> tempvec;
        vector<vector<int>> allpath;
        sps(root, sum, tempvec, allpath);
        return allpath;
    }
    
    // train of thought
    //
    void sps(TreeNode* root, int sum, vector<int> &pvec, vector<vector<int>> &allpath) {
        if(!root) return;
        
        if(root->val == sum && !root->left && !root->right) {
            pvec.push_back(root->val);
            allpath.push_back(pvec);
            pvec.pop_back();
            return;
        } 
        
        pvec.push_back(root->val);
        sps(root->left, sum-root->val, pvec, allpath);
        sps(root->right, sum-root->val, pvec, allpath);
        pvec.pop_back();
    }
};

 

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