LeetCode No.257 Binary Tree Paths

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"]

====================================================================================
题目链接：https://leetcode.com/problems/binary-tree-paths/

题目大意：求出二叉树中所有从头结点到叶子节点的路径。

思路：递归，对二叉树进行深搜，到达叶子节点的时候就记录下来。

注意点：将整数转成字符串的时候注意

附上代码：

/** * 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> ans ;        if ( root == NULL )            return ans ;        string s = "" ;        s += intToString ( root -> val ) ;        createPaths ( root , s , ans ) ;        return ans ;    }private :    void createPaths ( TreeNode* root , string s , vector <string>& ans )    {        if ( root -> left == NULL && root -> right == NULL )        {            ans.push_back ( s ) ;            return ;        }        s += "->" ;        if ( root -> left )        {            string str = s + intToString ( root -> left -> val ) ;            createPaths ( root -> left , str , ans ) ;        }        if ( root -> right )        {            string str = s + intToString ( root -> right -> val ) ;            createPaths ( root -> right , str , ans ) ;        }    }    string intToString ( int n )    {        if ( n == 0 )            return "0" ;        if ( n < 0 )            return "-" + intToString ( -n ) ;        string ans = "" ;        while ( n )        {            ans = char ( n % 10 + '0' ) + ans ;            n /= 10 ;        }        return ans ;    }};