Medium： Binary Tree Paths Add to List

257. Binary Tree Paths Add to List
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Total Accepted: 102130
Total Submissions: 276990
Difficulty: Easy
Contributor: LeetCode
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"]

代码如下：

class Solution {
public:
    void binaryTreePaths(vector<string>& result, TreeNode* root, string t) {
        if(!root->left && !root->right) {
            result.push_back(t);
            return;
        }
        if(root->left) binaryTreePaths(result, root->left, t + "->" + to_string(root->left->val));
        if(root->right) binaryTreePaths(result, root->right, t + "->" + to_string(root->right->val));
    }

    vector<string> binaryTreePaths(TreeNode* root) {
        vector<string> result;
        if(!root) return result; 
        binaryTreePaths(result, root, to_string(root->val));
        return result;
    }
}；

• 运用二叉树解题常用的递归思路，将复杂的问题简单化。
• 将每个结点的元素转化为一个string类放于t中，再一个一个递归的压入result，再返回。