JackZhangNJU的专栏

Given a non-empty integer array, find the minimum number of moves required to make all array elements equal, where a move is incrementing a selected element by 1 or decrementing a selected element by ...

Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle. Example 1: ...

Given an array which consists of non-negative integers and an integer m, you can split the array into m non-empty continuous subarrays. Write an algorithm to minimize the largest sum among these m sub

A city’s skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Now suppose you are given the locations and height of all the buildings as

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn’t one, return 0 instead.For example, given the arr

Given a linked list, determine if it has a cycle in it.Follow up: Can you solve it without using extra space?本题就是判断链表是否存在循环，这个方法很棒，说实话我自己是想不到的。代码如下：/*class ListNode { int val; Li

Given a linked list, return the node where the cycle begins. If there is no cycle, return null.Note: Do not modify the linked list.Follow up: Can you solve it without using extra space?和上一道题不一样

Define S = [s,n] as the string S which consists of n connected strings s. For example, [“abc”, 3] =”abcabcabc”.On the other hand, we define that string s1 can be obtained from string s2 if we can re...

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, ...

We are playing the Guess Game. The game is as follows:I pick a number from 1 to n. You have to guess which number I picked.Every time you guess wrong, I’ll tell you whether the number is higher or

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 follo

Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.You should try to do it in p

You have k lists of sorted integers in ascending order. Find the smallest range that includes at least one number from each of the k lists.We define the range [a,b] is smaller than range [c,d] if b-...

Given a non-negative integer c, your task is to decide whether there’re two integers a and b such that a2 + b2 = c.Example 1: Input: 5 Output: True Explanation: 1 * 1 + 2 * 2 = 5 Example 2: Inp...

For an integer n, we call k>=2 a good base of n, if all digits of n base k are 1.Now given a string representing n, you should return the smallest good base of n in string format. Example 1: I...

Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle value.Examples: [2,3,4] , the median i

Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.Your task is to find the smallest possible length of a ...

Given a singly linked list, determine if it is a palindrome.Follow up: Could you do it in O(n) time and O(1) space?建议和leetcode 680. Valid Palindrome II 去除一个字符的回文字符串判断 + 双指针 一起学习反转链表判断即可。代码如下：...

Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome.Example 1: Input: “aba” Output: True Example 2: Input: “abca” Output: True Explanat...

Nearly every one have used the Multiplication Table. But could you find out the k-th smallest number quickly from the multiplication table?Given the height m and the length n of a m * n Multiplicati...

Given two integers n and k, you need to construct a list which contains n different positive integers ranging from 1 to n and obeys the following requirement: Suppose this list is [a1, a2, a3, … , a...

Given a sorted array, two integers k and x, find the k closest elements to x in the array. The result should also be sorted in ascending order. If there is a tie, the smaller elements are always prefe...

Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repe...

You are given n pairs of numbers. In every pair, the first number is always smaller than the second number.Now, we define a pair (c, d) can follow another pair (a, b) if and only if b < c. Chain ...

The set S originally contains numbers from 1 to n. But unfortunately, due to the data error, one of the numbers in the set got duplicated to another number in the set, which results in repetition of o...

You are given an array of positive and negative integers. If a number n at an index is positive, then move forward n steps. Conversely, if it’s negative (-n), move backward n steps. Assume the first e...

Given an array of characters, compress it in-place.The length after compression must always be smaller than or equal to the original array.Every element of the array should be a character (not int...

Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area.For example, given the following matrix:1 0 1 0 0 1 0 1 1 1 1 1 1 1 1 1 0 0

Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lin

Given a sorted linked list, delete all duplicates such that each element appear only once.For example, Given 1->1->2, return 1->2. Given 1->1->2->3->3, return 1->2->3.这道题很简单，就是取出链表的重复元素，遍历一次即可。代码如下：

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example, Given 1->2->3->3->4->4->5, return 1->2->5. Given 1->1->1->2

Reverse a singly linked list.反转链表，我这里是采用头插法来实现反转链表。代码如下：/*class ListNode{ int val; ListNode next; ListNode(int x) { val = x; }}*/public class Solution{ public ListNode revers

Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with another chara

Write a program to find the node at which the intersection of two singly linked lists begins.For example, the following two linked lists:A: a1 → a2 ...

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”, ““]

Sort a linked list in O(n log n) time using constant space complexity.本题就是考察的是链表的归并排序。代码如下：/*class ListNode { int val; ListNode next; ListNode(int x) { val = x; }}*/public class So

Given a singly linked list L: L0?L1?…?Ln-1?Ln, reorder it to: L0?Ln?L1?Ln-1?L2?Ln-2?…You must do this in-place without altering the nodes’ values.For example, Given {1,2,3,4}, reorder it to {1,4,2,3}

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.k is a positive integer and is less than or equal to the length of the linked list. If the number of nod

Given a linked list, swap every two adjacent nodes and return its head.For example, Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant space. You may no

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.根据一个排序好的链表构造二叉平衡树，这个问题的重点是找到中间元素，使用双指针即可。建议和 leetcode 108. Convert Sorted Array to Binary Se