Question: Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2], [5,8,4,5] ] Anwser 1: [cpp] /** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: void calPath(TreeNode *root, int sum, vector<int> tmp, vector< vector<int> > &ret){ if(root == NULL){ return; } tmp.push_back(root->val); if(sum == root->val && root->left == NULL && root->right == NULL){ ret.push_back(tmp); } calPath(root->left, sum - root->val, tmp, ret); calPath(root->right, sum - root->val, tmp, ret); tmp.pop_back(); } vector<vector<int> > pathSum(TreeNode *root, int sum) { // Start typing your C/C++ solution below // DO NOT write int main() function vector< vector<int> > ret; if(root == NULL) { return ret; } vector<int> tmp; calPath(root, sum, tmp, ret); return ret; } }; Anwser 2: [cpp] /** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: void calPath(TreeNode *root, int sum, vector<int> tmp, vector< vector<int> > &ret){ if(root == NULL){ return; } tmp.push_back(root->val); if(sum == root->val && root->left == NULL && root->right == NULL){ ret.push_back(tmp); tmp.pop_back(); // pop tmp vector return; } calPath(root->left, sum - root->val, tmp, ret); calPath(root->right, sum - root->val, tmp, ret); tmp.pop_back(); } vector<vector<int> > pathSum(TreeNode *root, int sum) { // Start typing your C/C++ solution below // DO NOT write int main() function vector< vector<int> > ret; if(root == NULL) { return ret; } vector<int> tmp; calPath(root, sum, tmp, ret); return ret; } };