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binaryTreePaths.cpp
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95 lines (85 loc) · 2.54 KB
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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) {}
* };
*/
class Solution {
public:
vector<string> TreePaths;
void DFS(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
class Solution {
public:
void binaryTreePathsHelper(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;
}
};