[勇者闯LeetCode] 257. Binary Tree Paths

[勇者闯LeetCode] 257. Binary Tree Paths

Description

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"]

Information

• Difficulty: Easy

Solution

遍历二叉树的过程中记录之前的路径，一旦遍历到叶子节点便将该路径加入到结果中。

C++ Code

/** * 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> result;        vector<TreeNode*> path;        binaryTreePathsRecu(root, &path, &result);        return result;    }    void binaryTreePathsRecu(TreeNode* node, vector<TreeNode*> *path, vector<string> *result) {        if (!node) {            return;        }        if (!node->left && !node->right) {            string ans = "";            for (const auto &n : *path) {                ans.append(to_string(n->val).append("->"));            }            result->emplace_back(move(ans.append(to_string(node->val))));        }        if (node->left) {            path->emplace_back(node);            binaryTreePathsRecu(node->left, path, result);            path->pop_back();        }        if (node->right) {            path->emplace_back(node);            binaryTreePathsRecu(node->right, path, result);            path->pop_back();        }    }};