leetcode 解题思路

You are given a0-indexedarray ofnintegersarr.Theintervalbetween two elements inarris defined as theabsolute differencebetween their indices. More formally, theintervalbetweenarr[i]andarr[j]is|i - j|.Returnan arrayintervalsof length...

Given an integer array (index from 0 to n-1, where n is the size of this array), and an query list. Each query has two integers[start, end]. For each query, calculate the sum number between index sta...

Return thelengthof the shortest, non-empty, contiguoussubarray ofAwith sum at leastK.If there is no non-empty subarray with sum at leastK, return-1.Example 1:Input: A = [1], K = 1Output: 1Example 2:Input: A = [1,2], K = 4Output: -1...

Given amatrix, and atarget, return the number of non-empty submatrices that sum totarget.A submatrixx1, y1, x2, y2is the set of all cellsmatrix[x][y]withx1 <= x <= x2andy1 <= y <= y2.Two submatrices(x1, y1, x2, y2)and(x1', y1',...

Given a non-empty 2D matrixmatrixand an integerk, find the max sum of a rectangle in thematrixsuch that its sum is no larger thank.Example:Input: matrix = [[1,0,1],[0,-2,3]], k = 2Output: 2 Explanation:Because the sum of rectangle [[0, 1], [-...

Given am x nmatrixmatand an integerthreshold. Return the maximum side-length of a square with a sum less than or equal tothresholdor return0if there is no such square.Example 1:Input: mat = [[1,1,3,2,4,3,2],[1,1,3,2,4,3,2],[1,1,3,2,4,3,2]],...

Given an array of integersarrand an integertarget.You have to findtwo non-overlapping sub-arraysofarreach with sum equaltarget. There can be multiple answers so you have to find an answer where the sum of the lengths of the two sub-arrays ismini...

Alice plays the following game, loosely based on the card game "21".Alice starts with0points, and draws numbers while she has less thanKpoints. During each draw, she gains an integer number of points randomly from the range[1, W], whereWis an int...

Given an array with n integers, you need to find if there are triplets (i, j, k) which satisfies following conditions:0 < i, i + 1 < j, j + 1 < k < n - 1 Sum of subarrays (0, i - 1), (i + 1, j - 1), (j + 1, k - 1) and (k + 1, n - 1) should b

Given a 2D matrixmatrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1,col1) and lower right corner (row2,col2).The above rectangle (with the red border) is defined by (row1, col1) =(2, 1)and (row2, col2) ...

Given a list ofnon-negativenumbers and a targetintegerk, write a function to check if the array has a continuous subarray of size at least 2 that sums up to a multiple ofk, that is, sums up to n*k where n is also aninteger.Example 1:Input: [23, ...

In a given arraynumsof positive integers, find three non-overlapping subarrays with maximum sum.Each subarray will be of sizek, and we want to maximize the sum of all3*kentries.Return the result as a list of indices representing the starting posit...

Some people will make friend requests. Thelist of their ages is given andages[i]is the age of theith person.Person A will NOT friend request person B (B != A) if any of the following conditions are true:age[B]<= 0.5 * age[A]+ 7 age[B]> a...

Implement the classProductOfNumbersthat supports two methods:1.add(int num)Adds the numbernumto the back of the current list of numbers.2.getProduct(int k)Returns the product of the lastknumbers in the current list. You can assume that alwa...

Given an array of integersnums, write a method that returns the "pivot" index of this array.We define the pivot index as the index where the sum of the numbers to the left of the index is equal to ...

Given an arraynumsand a target valuek, find the maximum length of a subarray that sums tok. If there isn't one, return 0 instead.Note:The sum of the entirenumsarray is guaranteed to fit withi...

Given an array of integers and an integerk, you need to find the total number of continuous subarrays whose sum equals tok.Example 1:Input:nums = [1,1,1], k = 2Output: 2思路：用prefixsum记得用n+1 s...

Given an integer arraynums, find the sum of the elements between indicesiandj(i≤j), inclusive.Example:Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -> 1sumRange(2, 5) -> -1sumRan

Interval SumGiven an integer array (index from 0 to n-1, where n is the size of this array), and an query list. Each query has two integers[start, end]. For each query, calculate the sum number bet...

Given am * nmatrixmatand an integerK, return a matrixanswerwhere eachanswer[i][j]is the sum of all elementsmat[r][c]fori - K <= r <= i + K, j - K <= c <= j + K, and(r, c)is a...

Given an array ofn * mmatrix, and a moving matrix window (sizek * k), move the window from top left to botton right at each iteration, find the maximum sum inside the window at each moving.Return...

Given an integer matrix, find a submatrix where the sum of numbers is zero. Your code should return the coordinate of the left-up and right-down number.If there are multiple answers, you can return ...

Given an integer array, find a subarray with sum closest to zero. Return the indexes of the first number and last number.ExampleExample1Input: [-3,1,1,-3,5] Output: [0,2]Explanation: [0,2],...

There is a stone game.At the beginning of the game the player picksnpiles of stones in a line.The goal is to merge the stones in one pile observing the following rules:At each step of the game,t...

There is a stone game.At the beginning of the game the player picks n piles of stonesin a circle.The goal is to merge the stones in one pile observing the following rules:At each step of the game...

Given an circular integer array (the next element of the last element is the first element), find a continuous subarray in it, where the sum of numbers is the biggest. Your code should return the inde...

Given an integer array, find a continuous subarray where the sum of numbers is the biggest. Your code should return the index of the first number and the index of the last number. (If their are duplic...

Given an positive integer arrayAand an interval. Return the number of subarrays whose sum is in the range of given interval.ExampleExample 1:Input: A = [1, 2, 3, 4], start = 1, end = 3Output...

Given an integer array, find a subarray where the sum of numbers iszero. Your code should return the index of the first number and the index of the last number.ExampleExample 1:Input: [-3, 1,...