leetcode 解题思路

Design a stack which supports the following operations.Implement theCustomStackclass:CustomStack(int maxSize)Initializes the object withmaxSizewhich is the maximum number of elements in the stack or do nothing if the stack reached themaxSize. vo...

Given an arrayAof integers, returntrueif and only if it is avalid mountain array.Recall that A is a mountain array if and only if:A.length >= 3 There exists someiwith0 < i< A.length - 1such that: A[0] < A[1] < ... A[i-1] <...

Write an iterator that iterates through a run-length encoded sequence.The iterator is initialized byRLEIterator(int[] A), whereAis a run-length encoding of somesequence. More specifically,for all eveni,A[i]tells us the number of times that the n...

We are given a listnumsof integers representing a list compressed with run-length encoding.Consider each adjacent pairof elements[freq, val] = [nums[2*i], nums[2*i+1]](withi >= 0). For each such pair, there arefreqelements with valuevalconc...

In an exam room, there areNseats in a single row, numbered0, 1, 2, ..., N-1.When a student enters the room, they must sit in the seat that maximizes the distance to the closest person. If there are multiple such seats, they sit in the seat with the l...

Given a stringsand a list of stringsdict, you need to add a closed pair of bold tag<b>and</b>to wrap the substrings in s that exist in dict. If two such substrings overlap, you need to wrap them together by only one pair of closed bold t...

Given an arraynumswithnintegers, your task is to check if it could become non-decreasing by modifyingat most1element.We define an array is non-decreasing ifnums[i] <= nums[i + 1]holds for everyi(0-based) such that(0<= i <= n - 2)....

Given an integer numbern, return the difference between the product of its digits and the sum of its digits.Example 1:Input: n = 234Output: 15 Explanation: Product of digits = 2 * 3 * 4 = 24 Sum of digits = 2 + 3 + 4 = 9 Result = 24 - 9 = 15思路.

Given a non-negative integernum, return the number of steps to reduce it to zero. If the current number is even, you have to divide it by 2, otherwise, you have to subtract 1 from it.Example 1:Input: num = 14Output: 6Explanation:Step 1) 14 is eve..

A matrix isToeplitzif every diagonal from top-left to bottom-right has the same element.Now given anM x Nmatrix, returnTrueif and only if the matrix isToeplitz.Example 1:Input:matrix = ...

Given an array of integers A, amoveconsists of choosing anyA[i], and incrementing it by1.Return the least number of moves to make every value inAunique.Input: [3,2,1,2,1,7] Output: 6 Explanati...

In a town, there areNpeople labelled from1toN. There is a rumor that one of these people is secretly the town judge.If thetown judge exists, then:The town judge trusts nobody. Everybody (e...

Give a number of arrays, find their intersection, and output their intersection size.ExampleExample 1: Input: [[1,2,3],[3,4,5],[3,9,10]] Output: 1 Explanation: Only '3' in all three arra...

Given an array arr[], find the maximum j – i such that arr[j] > arr[i]Given an array arr[], find the maximum j – i such that arr[j] > arr[i].Examples: Input: {34, 8, 10, 3, 2, 80, 30, 33,

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as poss...

 Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complete at most two transactions.Note:You may no...

Given two arrays, write a function to compute their intersection.Example 1:Input: nums1 = [1,2,2,1], nums2 = [2,2]Output: [2]Example 2:Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]Output: [...

Given an integer array, find three numbers whose product is maximum and output the maximum product.Example 1:Input: [1,2,3]Output: 6Example 2:Input: [1,2,3,4]Output: 24Note:The lengt...

Given an array of sizen, find the majority element. The majority element is the element that appearsmore than⌊ n/2 ⌋times.You may assume that the array is non-empty and the majority element alwa...

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.Hint:How many majority elements could it possibly...

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.Find all the elements of [1, n] inclusive that do not appear in this array.Coul...

Given an array of integers, 1 ≤ a[i] ≤n(n= size of array), some elements appeartwiceand others appearonce.Find all the elements that appeartwicein this array.Could you do it without extra ...

Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array A = [1,1,1,2,2,3],Your function should return length = 5, and A is now [1,1,2,2,3]....

Say you have an array for which theithelement is the price of a given stock on dayi.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock)...

Given an array ofnintegers wheren> 1,nums, return an arrayoutputsuch thatoutput[i]is equal to the product of all the elements ofnumsexceptnums[i].Solve itwithout divisionand in O(n)....

This is afollow upofShortest Word Distance. The only difference is nowword1could be the same asword2.Given a list of words and two wordsword1andword2, return the shortest distance betwe

Given a sorted integer array where the range of elements are [lower,upper] inclusive, return its missing ranges.For example, given[0, 1, 3, 50, 75],lower= 0 andupper= 99, return["2", "4->49

Givennnon-negative integers representing an elevation map where the width of each bar is1, compute how much water it is able to trap after raining.ExampleExample 1:Input: [0,1,0]Output: 0...

You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Follow up:Could you do this in-place?思路：上下左右替换，layer 注意offset = i - first;是算与前面的差距。然后就

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.For example,Given the following matrix:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]You

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.思路：用第一行，第一列来记录信息。然后首先略过第一行第一列，进行设置。然后再看第一行第一列是否要设置0；public class Solution { public

Given two sorted integer arraysnums1andnums2, mergenums2intonums1as one sorted array.Note:The number of elements initialized innums1andnums2aremandnrespectively. You may assume tha...

Given an array and a value, remove all instances of that value in place and return the new length.Do not allocate extra space for another array, you must do this in place with constant memory.T...

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.思路：刚开始想的...

Given an integer n, generate a square matrix filled with elements from 1 ton2 in spiral order.For example,Given n = 3,You should return the following matrix:[ [ 1, 2, 3 ], [ 8, 9, 4 ], [

Suppose you are at a party with n people (labeled from 0 to n - 1) and among them, there may exist one celebrity. The definition of a celebrity is that all the other n - 1 people know him/her but he/s...

Given a list of words and two wordsword1andword2, return the shortest distance between these two words in the list.For example,Assume that words =["practice", "makes", "perfect", "coding", "

The API:int read4(char *buf)reads 4 characters at a time from a file.The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the

The API:int read4(char *buf)reads 4 characters at a time from a file.The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the

Determine if a Sudoku is valid, according to:Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character'.'.A partially filled sud...