257. Binary Tree Paths

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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"]

solution:

/** * 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> res;        traverse(root, res);        return res;    }    void traverse(TreeNode *root, vector<string> &res){        if(!root) return;        if(res.size()==0) res.push_back(string());        if(!root->left&&!root->right){            res[res.size()-1] += to_string(root->val);        }         if(root->left&&!root->right){            res[res.size()-1] += to_string(root->val)+"->";            traverse(root->left,res);        }        if(root->right&&!root->left){            res[res.size()-1] += to_string(root->val)+"->";            traverse(root->right,res);        }        if(root->right&&root->left){            res[res.size()-1] += to_string(root->val)+"->";            string tmp = res[res.size()-1];            traverse(root->left,res);            res.push_back(tmp);            traverse(root->right,res);        }    }};

心得：思路比较简单

运行速度快

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