leetcode/algorithms/cpp/binaryTreePaths/binaryTreePaths.cpp at master · haoel/leetcode · GitHub

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// Source : https://leetcode.com/problems/binary-tree-paths/
// Author : Calinescu Valentin, Hao Chen
// Date : 2015-10-23

/***************************************************************************************
 *
 * Given a binary tree, return all root-to-leaf paths.
 *
 * For example, given the following binary tree:
 *
 * 1
 * / \
 * 2 3
 * \
 * 5
 *
 * All root-to-leaf paths are:
 * ["1->2->5", "1->3"]
 *
 * Credits:
 * Special thanks to @jianchao.li.fighter for adding this problem and creating all test
 * cases.
 *
 ***************************************************************************************/
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * TreeNode *left;
 * TreeNode *right;
 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
*/
classSolution {
public:
 vector<string> TreePaths;
voidDFS(TreeNode* node, string answer)
 {
 answer += "->" + to_string(node->val);
if(node->left == NULL && node->right == NULL)
 TreePaths.push_back(answer);
else
 {
if(node->left != NULL)
DFS(node->left, answer);
if(node->right != NULL)
DFS(node->right, answer);
 }
 }
 vector<string> binaryTreePaths(TreeNode* root) {
if(root != NULL)
 {
DFS(root, "");
for(int i = 0; i < TreePaths.size(); i++)
 TreePaths[i].erase(TreePaths[i].begin(), TreePaths[i].begin() + 2);
 }
return TreePaths;
 }
};


// Another more clear DFS implementation

classSolution {
public:
voidbinaryTreePathsHelper(TreeNode* root, vector<int> solution, vector<string>& result ) {
if (!root) return;

 solution.push_back(root->val);

//meet the leaf node, shape a path into the result
if (root->left==NULL && root->right==NULL){
if(solution.size()>0){
 stringstream ss;
for(int i=0; i<solution.size(); i++){
 ss << solution[i] << (i<solution.size()-1 ? "->":"");
 }
 result.push_back(ss.str());
 }
return;
 }

binaryTreePathsHelper(root->left, solution, result);
binaryTreePathsHelper(root->right, solution, result);

 }
 vector<string> binaryTreePaths(TreeNode* root) {
 vector<string> result;
 vector<int> solution;
binaryTreePathsHelper(root, solution, result);
return result;
 }
};