力扣-257题二叉树的所有路径（C++）- 回溯+递归+有价值

柔情只为你懂 2022-09-10 10:13 130阅读 0赞

题目链接：[https://leetcode-cn.com/problems/binary-tree-paths/][https_leetcode-cn.com_problems_binary-tree-paths]  
题目如下：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16]  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16 1]

/**
     * Definition for a binary tree node.
     * struct TreeNode {
     *     int val;
     *     TreeNode *left;
     *     TreeNode *right;
     *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
     *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
     *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
     * };
     */
    class Solution {
        
    public:
        vector<string> binaryTreePaths(TreeNode* root) {
        
            vector<string> result;
            vector<int> path;
            if(root==NULL) return result;
            dfs(root,path,result);
            return result;
        }
    
        void dfs(TreeNode* root,vector<int>& path,vector<string>& result){
        
            
            path.push_back(root->val);
    
            //终止条件：当找到叶子节点的时候，就将路径放入到result中
            //即root->left==NULL&&root->right==NULL
            if(root->left==NULL&&root->right==NULL){
        //遇到叶子节点，将路径放入result
                string str_path="";
                for(int e:path)
                str_path+=to_string(e)+"->";
    
                str_path[str_path.size()-1]=str_path[str_path.size()-2]=0;//去掉多余的->
    
                result.push_back(str_path);
                return ;
            }
    
            //单层逻辑（前序遍历——根左右）
            if(root->left){
        
                dfs(root->left,path,result);
                path.pop_back();
            }
            if(root->right){
        
                dfs(root->right,path,result);
                path.pop_back();
            }
    
        }
    };

[https_leetcode-cn.com_problems_binary-tree-paths]: https://leetcode-cn.com/problems/binary-tree-paths/
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220829/c20d2c9100da48b0b7f79f76f128c1bf.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220829/e3928d986cb9418e8b397a1a3e0d2565.png