[力扣题解] 257. 二叉树的所有路径

题目：257. 二叉树的所有路径

思路

前序遍历

代码

/**
 * 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> result;
    
    void travel(TreeNode* cur, vector<int>& path)
    {
        int i;
        if(cur == NULL)
        {
            return;
        }
        path.push_back(cur->val);
        if(cur->left == NULL && cur->right == NULL)
        {
            string temp;
            //
            for(i = 0; i < path.size()-1; i++)
            {
                temp.append(to_string(path[i]) + "->");
            }
            temp.append(to_string(path[i]));
            result.push_back(temp);
        }
        if(cur->left)
        {
            travel(cur->left, path);
            path.pop_back();
        }
        if(cur->right)
        {
            travel(cur->right, path);
            path.pop_back();
        }
    }

    vector<string> binaryTreePaths(TreeNode* root) {
        vector<int> path;
        if(root == NULL)
        {
            return result;
        }
        travel(root, path);
        return result;
    }
};