#Arrays

In a sorted array, determine the first and last index of a specified element. Your solution should be efficient, utilizing binary search where appropriate.

Given an array of integers, identify four numbers that sum up to zero. Consider all possible combinations and provide an efficient algorithm to achieve this.

Calculate the sum of the minimum elements of all subarrays in a given array. Your approach should aim for O(n) time complexity.

Solve the circular tour problem where you need to determine if a tour can be completed within given petrol and distance constraints. Provide your algorithm and reasoning.

How do you find a missing number in an array given overflow constraints? Discuss your approach.