1.描述

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"]

2.分析

3.代碼

/**
 * 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> binaryTreePaths(TreeNode* root) {
        vector<string> vec;
        if (root == NULL) return vec;
        
        stringstream ss;
        ss << root->val;
        string str = ss.str();
        
        if (root->left == NULL && root->right == NULL) {
            vec.push_back(str);
        }
        
        if (root->left) visitTreeNodes(root->left, vec, str);
        if (root->right) visitTreeNodes(root->right, vec, str);
        
        return vec;
    }
    
private:
    void visitTreeNodes(TreeNode* root, vector<string> &vec, string str) {
        str += "->";
        stringstream ss;
        ss << root->val;
        str += ss.str();
        if (root->left == NULL && root->right == NULL) {
            vec.push_back(str);
            return ;
        }
        
        if (root->left) visitTreeNodes(root->left, vec, str);
        if (root->right) visitTreeNodes(root->right, vec, str);
    }
};