Ruizhi Ma's Blog

Problem 104

Maximum Depth of Binary Tree

问题描述 https://leetcode.com/problems/maximum-depth-of-binary-tree/ 解决思路用递归解决DFS（深度优先）问题。递归的最重要的核心点就是两个：1. 递归出口是什么 2. 递归公式是什么。在这里，递归的出口显然是root没有左右孩子；公式则是比较左右孩子最多的节点作为返回值，而找到左右孩子最多的节点有需要调用maxDept...

Posted by Ruizhi Ma on August 17, 2019

Problem 111

Minimum Depth of Binary Tree

问题描述 https://leetcode.com/problems/minimum-depth-of-binary-tree/ 解决思路临界条件：root == null 递归公式：返回左右子树最小的那个，长度加1（因为还有root自己）特殊状态：左右子树有一个为空树，则应该返回另一边的子树，因为深度并不在此处停止计算代码 /** * Definition fo...

Posted by Ruizhi Ma on August 16, 2019

Problem 96

Unique Binary Search Trees

问题描述 https://leetcode.com/problems/unique-binary-search-trees/ 代码 class Solution { public int numTrees(int n) { if(n < 1) return 0; int[] nums = new int[n + 1]; nums...

Posted by Ruizhi Ma on August 15, 2019

Problem 100

Same Tree

问题描述 https://leetcode.com/problems/same-tree/ 解决思路递归遍历树就可以，比较简单。代码 /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode rig...

Posted by Ruizhi Ma on August 15, 2019

Problem 94

Binary Tree Inorder Traversal

问题描述 https://leetcode.com/problems/binary-tree-inorder-traversal/ 代码 /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode righ...

Posted by Ruizhi Ma on August 14, 2019

Problem 91

Decode Ways

问题描述 https://leetcode.com/problems/decode-ways/ 代码 class Solution { public int numDecodings(String s) { //corner case if(s == null || s.length() == 0) return 0; int siz...

Posted by Ruizhi Ma on August 14, 2019

Problem 92

Reverse Linked List II

问题描述 https://leetcode.com/problems/reverse-linked-list-ii/ 代码 /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { va...

Posted by Ruizhi Ma on August 13, 2019

Problem 90

Subsets II

问题描述 https://leetcode.com/problems/subsets-ii/ 解决思路同78题，需要加入判断重复。代码 class Solution { public List<List<Integer>> subsetsWithDup(int[] nums) { List<List<Integer>&...

Posted by Ruizhi Ma on August 13, 2019

Problem 206

Reverse Linked List

问题描述 https://leetcode.com/problems/reverse-linked-list/ 代码 /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { val =...

Posted by Ruizhi Ma on August 13, 2019

Problem 89

Gray Code

问题描述 https://leetcode.com/problems/gray-code/ 解决思路 https://leetcode-cn.com/problems/gray-code/solution/xiang-xi-tong-su-de-si-lu-fen-xi-duo-jie-fa-by–12/ 代码 class Solution { public List<In...

Posted by Ruizhi Ma on August 12, 2019

Ruizhi Ma's Blog

Problem 104

Maximum Depth of Binary Tree

Problem 111

Minimum Depth of Binary Tree

Problem 96

Unique Binary Search Trees

Problem 100

Same Tree

Problem 94

Binary Tree Inorder Traversal

Problem 91

Decode Ways

Problem 92

Reverse Linked List II

Problem 90

Subsets II

Problem 206

Reverse Linked List

Problem 89

Gray Code

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