Leetcode

307. Range Sum Query - Mutable Given an integer array nums, handle multiple queries of the following types: Update the value of an element in nums. Calculate the sum of the elements of nums between indices left and right inclusive where left <= right. Implement the NumArray class: NumArray(int[] nums) Initializes the object with the integer array nums. void update(int index, int val) Updates the value of nums[index] to be val. int sumRange(int left, int right) Returns the sum of the elements of nums between indices left and right inclusive (i.e. nums[left] + nums[left + 1] + … + nums[right]). Example 1: Input ["NumArray", "sumRange", "update", "sumRange"] [[[1, 3, 5]], [0, 2], [1, 2], [0, 2]] Output [null, 9, null, 8] Explanation NumArray numArray = new NumArray([1, 3, 5]); numArray.sumRange(0, 2); // return 1 + 3 + 5 = 9 numArray.update(1, 2); // nums = [1, 2, 5] numArray.sumRange(0, 2); // return 1 + 2 + 5 = 8 Constraints: ...

304. Range Sum Query 2D - Immutable Given a 2D matrix matrix, handle multiple queries of the following type: Calculate the sum of the elements of matrix inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). Implement the NumMatrix class: NumMatrix(int[][] matrix) Initializes the object with the integer matrix matrix. int sumRegion(int row1, int col1, int row2, int col2) Returns the sum of the elements of matrix inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). Example 1: Input ["NumMatrix", "sumRegion", "sumRegion", "sumRegion"] [[[[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]], [2, 1, 4, 3], [1, 1, 2, 2], [1, 2, 2, 4]] Output [null, 8, 11, 12] Explanation NumMatrix numMatrix = new NumMatrix([[3, 0, 1, 4, 2], [5, 6, 3, 2, 1], [1, 2, 0, 1, 5], [4, 1, 0, 1, 7], [1, 0, 3, 0, 5]]); numMatrix.sumRegion(2, 1, 4, 3); // return 8 (i.e sum of the red rectangle) numMatrix.sumRegion(1, 1, 2, 2); // return 11 (i.e sum of the green rectangle) numMatrix.sumRegion(1, 2, 2, 4); // return 12 (i.e sum of the blue rectangle) ...

962. Maximum Width Ramp A ramp in an integer array nums is a pair (i, j) for which i < j and nums[i] <= nums[j]. The width of such a ramp is j - i. Given an integer array nums, return the maximum width of a ramp in nums. If there is no ramp in nums, return 0. Example 1: Input: nums = [6,0,8,2,1,5] Output: 4 Explanation: The maximum width ramp is achieved at (i, j) = (1, 5): nums[1] = 0 and nums[5] = 5. Example 2: Input: nums = [9,8,1,0,1,9,4,0,4,1] Output: 7 Explanation: The maximum width ramp is achieved at (i, j) = (2, 9): nums[2] = 1 and nums[9] = 1. Constraints: ...

319. Bulb Switcher There are n bulbs that are initially off. You first turn on all the bulbs, then you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it’s off or turning off if it’s on). For the ith round, you toggle every i bulb. For the nth round, you only toggle the last bulb. Return the number of bulbs that are on after n rounds. ...

581. Shortest Unsorted Continuous Subarray Given an integer array nums, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order. Return the shortest such subarray and output its length. Example 1: Input: nums = [2,6,4,8,10,9,15] Output: 5 Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order. Example 2: Input: nums = [1,2,3,4] Output: 0 Example 3: Input: nums = [1] Output: 0 Constraints: ...

907. Sum of Subarray Minimums Given an array of integers arr, find the sum of min(b), where b ranges over every (contiguous) subarray of arr. Since the answer may be large, return the answer modulo 109 + 7. Example 1: Input: arr = [3,1,2,4] Output: 17 Explanation: Subarrays are [3], [1], [2], [4], [3,1], [1,2], [2,4], [3,1,2], [1,2,4], [3,1,2,4]. Minimums are 3, 1, 2, 4, 1, 1, 2, 1, 1, 1. Sum is 17. Example 2: Input: arr = [11,81,94,43,3] Output: 444 Constraints: ...

398. Random Pick Index Given an integer array nums with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array. Implement the Solution class: Solution(int[] nums) Initializes the object with the array nums. int pick(int target) Picks a random index i from nums where nums[i] == target. If there are multiple valid i’s, then each index should have an equal probability of returning. Example 1: Input ["Solution", "pick", "pick", "pick"] [[[1, 2, 3, 3, 3]], [3], [1], [3]] Output [null, 4, 0, 2] Explanation Solution solution = new Solution([1, 2, 3, 3, 3]); solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning. solution.pick(1); // It should return 0. Since in the array only nums[0] is equal to 1. solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning. Constraints: ...

364. Nested List Weight Sum II You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. The depth of an integer is the number of lists that it is inside of. For example, the nested list [1,[2,2],[[3],2],1] has each integer’s value set to its depth. Let maxDepth be the maximum depth of any integer. ...

901. Online Stock Span Design an algorithm that collects daily price quotes for some stock and returns the span of that stock’s price for the current day. The span of the stock’s price today is defined as the maximum number of consecutive days (starting from today and going backward) for which the stock price was less than or equal to today’s price. For example, if the price of a stock over the next 7 days were [100,80,60,70,60,75,85], then the stock spans would be [1,1,1,2,1,4,6]. Implement the StockSpanner class: ...

1762. Buildings With an Ocean View There are n buildings in a line. You are given an integer array heights of size n that represents the heights of the buildings in the line. The ocean is to the right of the buildings. A building has an ocean view if the building can see the ocean without obstructions. Formally, a building has an ocean view if all the buildings to its right have a smaller height. ...