shawnlyu

September 21, 2020September 21, 2020

[Leetcode]1589. Maximum Sum Obtained of Any Permutation

We have an array of integers, nums, and an array of requests where requests[i] = [start_i, end_i]. The i^th request asks for the sum of nums[start_i] + nums[start_i + 1] + ... + nums[end_i - 1] + nums[end_i]. Both start_i and end_i are 0-indexed.
Return the maximum total sum of all requests among all permutations of nums.
Since the answer may be too large, return it modulo 10⁹ + 7.

September 19, 2020September 19, 2020

[Leetcode]1590. Make Sum Divisible by P

Given an array of positive integers nums, remove the smallest subarray (possibly empty) such that the sum of the remaining elements is divisible by p. It is not allowed to remove the whole array.
Return the length of the smallest subarray that you need to remove, or -1 if it's impossible.
A subarray is defined as a contiguous block of elements in the array.

September 18, 2020September 18, 2020

[Leetcode]33. Search in Rotated Sorted Array

You are given an integer array nums sorted in ascending order, and an integer target.
Suppose that nums is rotated at some pivot unknown to you beforehand (i.e., [0,1,2,4,5,6,7]might become [4,5,6,7,0,1,2]).
If target is found in the array return its index, otherwise, return -1.

September 16, 2020September 16, 2020

[Leetcode]421. Maximum XOR of Two Numbers in an Array

Given a non-empty array of numbers, a₀, a₁, a₂, … , a_n-1, where 0 ≤ a_i < 2³¹.
Find the maximum result of a_i XOR a_j, where 0 ≤ i, j < n.
Could you do this in O(n) runtime?

September 15, 2020September 15, 2020

Disjoint Set – Union & Find

In computer science, a disjoint-set data structure … is a data structure that stores a collection of disjoint (non-overlapping) sets. … It provides operations for adding new sets, merging sets (replacing them by their union), and finding a representative member of a set.
Source: https://en.wikipedia.org/wiki/Disjoint-set_data_structure

September 15, 2020September 15, 2020

Minimum Spanning Tree – Prim

A minimum spanning tree (MST) or minimum weight spanning tree is a subset of the edges of a connected, edge-weighted undirected graph that connects all the vertices together, without any cycles and with the minimum possible total edge weight.
Source: https://en.wikipedia.org/wiki/Minimum_spanning_tree

September 11, 2020September 11, 2020

[Leetcode]640. Solve the Equation

Solve a given equation and return the value of x in the form of string "x=#value". The equation contains only '+', '-' operation, the variable x and its coefficient.
If there is no solution for the equation, return "No solution".
If there are infinite solutions for the equation, return "Infinite solutions".
If there is exactly one solution for the equation, we ensure that the value of x is an integer.

September 11, 2020September 11, 2020

[Leetcode]282. Expression Add Operators

Given a string that contains only digits 0-9 and a target value, return all possibilities to add binaryoperators (not unary) +, -, or * between the digits so they evaluate to the target value.