Problems
October 18, 2022
Reduction operations to make the array elements equal
We will sort the array in descending order, then iterate over the array and count the number of elements that are less than the current element. Finally return the sum of the counts. Time...
ReadOctober 17, 2022
Best sightseeing pair
Count the current best score in all previous sightseeing spot. Note that, as we go further, the score of previous spot decrement. cur will record the best score that we have met. We iterate each...
ReadOctober 16, 2022
Find numbers with even number of digits
Given an array nums of integers, return how many of them contain an even number of digits. We will use a helper function to count the number of digits of each number. Then iterate over...
October 16, 2022
Delete leaves with a given value
We will use recursion to solve this problem. If the current node is a leaf and its value is the target value, we will return None. Otherwise, we will recursively call the function on the...
October 16, 2022
Minimum difficulty of a job schedule
We will apply DFS to find the the minimum difficulty if start work at ith job with d days left. If d = 1, only one day left, we have to do all jobs, return the maximum difficulty of...
October 16, 2022
Convert binary number in a linked list to integer
We will use a variable res to store the result. We will iterate over the linked list, and for each node, we will shift res to the left by 1 bit, and add the value of the...
October 15, 2022
String compression II
Start from the beginning of the s, you would meet two situations: The next character is the same as the last one, e.g. "aaa" with the next one still "a". The former characters would be "a3", so you...
ReadOctober 14, 2022
Delete the middle node of a linked list
We will take a two pointer approach to find the middle node, and then we will delete the middle node. The first pointer will move one step at a time, and the second pointer will move two steps at a...
ReadOctober 13, 2022
Find missing observations
We are given an array of n integers. We are also given m missing values. We need to find all the possible values that can be assigned to the missing values such that the...
October 13, 2022
Shift 2d grid
We are given a 2d grid of size m x n and an integer k. We need to shift the grid k times. In one shift operation, we shift the grid by one cell to the right....