Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is. You may not alter the values in the nodes, only nod…

问题描述:1->2->3->4,假设k=2进行反转,得到2->1->4->3:k=3进行反转,得到3->2->1->4 算法思想:基本操作就是链表反转,将k个元素当作滑动窗口,依次进行反转. public class ReverseNodesInKGroup { public ListNode reverseKGroup(ListNode head, int k) { if (k == 1 || head == null || head.next ==…

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. Each number in C may only be used once in the combination. Note: All numbers (including target) will be posi…

Write a program to solve a Sudoku puzzle by filling the empty cells. Empty cells are indicated by the character '.'. You may assume that there will be only one unique solution. A sudoku puzzle... ...and its solution numbers marked in red. 题意分析: 本题是要解…

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. You may assume no duplicates in the array. Here are few examples.[1,3,5,6], 5 → 2[1,3,5,6], 2 →…

算法和数据结构知识点图 首先,了解算法和数据结构有哪些知识点,在后面的学习中有 大局观,对学习和刷题十分有帮助. 下面是我花了一天时间花的算法和数据结构的知识结构,大家可以看看. 后面是为大家 精心挑选的LeetCode题单,并根据题目知识点的类型分好了类别,大家可以根据每个知识点,进行有针对性的刷题. 数据结构 数组&双指针 LeetCode 1. 两数之和 LeetCode 4. 寻找两个正序数组的中位数 LeetCode 15. 三数之和 LeetCode 75. 颜色分类 LeetCod…

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 题解:最开始用了最naive的方法,每次在k个链表头中找出最小的元素,插入到新链表中.结果果断TLE了. 分析一下,如果这样做,每取出一个节点,要遍历k个链表一次,假设k个链表一共有n个节点,那么就需要O(nk)的时间复杂度. 参考网上的代码,找到了用最小堆的方法.维护一个大小为k的最小堆,存放当前k…

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is. You may not alter the values in the nodes, only nod…

[Q7]  把数倒过来 Given a 32-bit signed integer, reverse digits of an integer. Example 1: Input: 123 Output: 321 Example 2: Input: -123 Output: -321 Example 3: Input: 120 Output: 21 Solution: https://leetcode.com/problems/reverse-integer/discuss/229800/Pyt…

Given a 32-bit signed integer, reverse digits of an integer. Example 1:                               Input: 123                       Output: 321 Example 2:                               Input: -123                      Output: -321 Example 3:     …

Reverse a singly linked list. Example:           Input: 1->2->3->4->5->NULL                   Output: 5->4->3->2->1->NULL Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both? 解…

Given a linked list, swap every two adjacent nodes and return its head. You may not modify the values in the list's nodes, only nodes itself may be changed. Example:          Given 1->2->3->4, you should return the list as 2->1->4->3. 将相…

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2", "1", "+", "3", "*"] -&g…

Given an input string, reverse the string word by word. For example,Given s = "the sky is blue",return "blue is sky the". 题解:用栈就行了 代码: class Solution { public: void reverseWords(string &s) { stack<string>st; string temp = &qu…

Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321 解题:设定一个变量sum存放反转后的答案,每次取输入x的最后一位n,并用sum = sum*10+n更新sum. 例如题设的数字123,初始sum为0,过程如下: 取末尾的3,sum=3,x=12 取末尾的2,sum=32,x=1 取末尾的1,sum=321,x=0 特别注意x一开始就是0的处理,直接返回0就可以了.…

Reverse a linked list from position m to n. Do it in-place and in one-pass. For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4, return 1->4->3->2->5->NULL. Note:Given m, n satisfy the following condition:1 ≤ m ≤ n ≤ lengt…

Write a function that reverses a string. The input string is given as an array of characters char[].Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.You may assume all the ch…

[Q1] Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice. Example: Given nums = [2, 7, 11…

[Q19] Given a linked list, remove the n-th node from the end of list and return its head. Example: Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5. Note: Giv…

[Q10] Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*'. '.' Matches any single character. '*' Matches zero or more of the preceding element. The matching should cover the entire input str…

[Q13] Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, w…

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. You may assume the two numbers…

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. Input: (2 -> 4 -> 3) + (5 -> 6 ->…

The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11.11 is read off as "two 1s" or 21.21 is read off as "one 2, then one 1" or 1211. Given an…

题目: There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to its next station (i+1). You begin the journey with…

称号 Rotate an array of n elements to the right by k steps. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. Note:Try to come up as many solutions as you can, there are at least 3 different ways to solve this…

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place. Example 1: Input: [   [1,1,1],   [1,0,1],   [1,1,1] ] Output: [   [1,0,1],   [0,0,0],   [1,0,1] ] Example 2: Input: [   [0,1,2,0],   [3,4,5,2],   [1,3,1,5]…

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. Example:Input: [   1->4->5,   1->3->4,   2->6 ] Output: 1->1->2->3->4->4->5->6 思路 这道题最简单的方法就是我们将K个链表中的所有数据都存进数组中,然后对数据进行…

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. Example:        Input: 1->2->4, 1->3->4              Output: 1->1->2->3->4->4 解决思路:最简单…

[Q4] There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). You may assume nums1 and nums2 cannot be both empty. Example 1: nums1 = […