Sort Colors - Leetcode 75 - Java

Learn how to solve the Leetcode problem of id 75, whose title is Sort Colors, using the Java programming language.

https://leetcode.com/problems/sort-colors

The Data Structures and Algorithms (DSA) lesson uses a three-pointer approach to solving the question using Java.

Since the zeroes need to be placed at the left-hand side of the resulting array, we use a pointer initialized to 0 to keep track of the index for the zeroes ("Zero Pointer"). Similarly, you create another pointer initialized to length of array minus one to keep track of the index for the twos ("Two Pointer").

With a separate index pointer ("Position Pointer") to traverse the array, you look at what integer you are faced with. It will be either 0, 1, or 2.

If it's 0, swap the element at the Zero Pointer with the current position and fill in with 0 at the Zero Pointer; increment both Zero Pointer and Position Pointer.

If it's 2, swap the element at the Two Pointer with the current position, filling with 2 the value at Two Pointer; decrement the Zero Pointer.

If you find one, simply increment the Position Pointer.

The time complexity for the solution is O(n) and its space complexity is O(1).

DSA problems are sometimes asked during tech job interviews for positions such as Software Engineer, so you can use the challenge to practice that skill.