[Java coding] leetcode notes

Start from Difficulty 1:

1, Remove specified elem from unsorted array: 2 pointers, one is to iterate all the elements in the array, the other is to increase if current value is not equal to specified element.

2, Remove duplicates from sorted array: still 2 pointers, compare current value with previous.

3, Remove 3rd duplicate from sorted array: on 2, have another var to store the appearance number.

4, Remove duplites from sorted linked list: prev & curr, then pay attention to null head input.

时间： 2024-12-12 16:46:21

[Java coding] leetcode notes的相关文章

Java for LeetCode 216 Combination Sum III

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1

Java for LeetCode 128 Longest Consecutive Sequence

Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example, Given [100, 4, 200, 1, 3, 2], The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4. Your algorithm should run i

Java for LeetCode 098 Validate Binary Search Tree

Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with keys

Java for LeetCode 057 Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge

Java for LeetCode 059 Spiral Matrix II

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ]] 解题思路: 参考Java for LeetCode 054 Spiral Matrix,修改下

Java for LeetCode 107 Binary Tree Level Order Traversal II

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example: Given binary tree {3,9,20,#,#,15,7}, 3 / 9 20 / 15 7 return its bottom-up level order trave

Java for LeetCode 108 Convert Sorted Array to Binary Search Tree

Given an array where elements are sorted in ascending order, convert it to a height balanced BST. 解题思路: 首先要理解,什么叫做height balanced BST Java for LeetCode 110 Balanced Binary Tree,然后就十分容易了,JAVA实现如下: public TreeNode sortedArrayToBST(int[] nums) { return

Java for LeetCode 090 Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example, If nums = [1,2,2], a soluti

Java for LeetCode 214 Shortest Palindrome

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu