day14 - 二叉树part01

zqh2023 / 2023-08-22 / 原文

144. 二叉树的前序遍历

详解

/**
 * 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:
    void search(TreeNode* node, vector<int>& result){
        if(!node)
            return;
        result.push_back(node->val);
        search(node->left, result);
        search(node->right, result);
    }

    vector<int> preorderTraversal(TreeNode* root) {
        vector<int> result;
        search(root, result);
        return result;
    }
};

145. 二叉树的后序遍历

/**
 * 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:
    void search(TreeNode* node, vector<int>& result){
        if(!node)
            return;
        search(node->left, result);
        search(node->right, result);
        result.push_back(node->val);
    }
    
    vector<int> postorderTraversal(TreeNode* root) {
        vector<int> result;
        search(root, result);
        return result;
    }
};

94. 二叉树的中序遍历

/**
 * 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:
    void search(TreeNode* node, vector<int>& result){
        if(!node)
            return;
        search(node->left, result);
        result.push_back(node->val);
        search(node->right, result);
    }
    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> result;
        search(root, result);
        return result;
    }
};