ALGORITHMS

Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.Find all the elements that appear twice in this array.

2. LEETCODE PROBLEM—Sort Colors: Sort Array of 0s,1s,2s without extra space and sorting algo:

Given an array with n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white and blue.
Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.

3. LEETCODE PROBLEM—Find Missing Number:

Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array.

4. FIND MISSING AND REPEATED NUMBER IN AN ARRAY :

Given an unsorted array of size n. Array elements are in the range from 1 to n. One number from set {1, 2, …n} is missing and one number occurs twice in the array. Find these two numbers.

5. LEETCODE PROBLEM—Maximum Subarray :

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

6. LEETCODE PROBLEM—Merged Intervals :

Given a collection of intervals, merge all overlapping intervals.
Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].