Given an integer array nums, where nums[i] is in the range nums[1,n], return all the missing numbers in the range [1,n] that do not

Given an integer array nums, containing n distinct numbers in the range 0 to n, return the only number in the range that is missing.

Given an array of integers nums, write an algorithm that returns true if any value appears at least twice in the array, and return false if

Given an integer array nums sorted in ascending order, move all single occurrences of elements in it to the beginning of the nums array

Given a m x n 2D binary array grid which represents of map of '1's (land) and '0's (water), return the number of islands in this grid.

Given a 2D m x n array grid containing only 1s (land) and 0s (water), count the number of islands in it. An island is surrounded by