The title of this LeetCode questions is very ambiguous and does not do a great job explaining what it actually does. All this interview question is asking you to do is move the zeros to the end of an array. That’s it. Before: After: 2-Pointer Step-By-Step (In-Place)

Essentially, this Leetcode question is asking “do the numbers in an array go up then go down“. It’s called a mountain array because if you draw a line tracing the path of the numbers it will look something like this: The following conditions must apply: Another way to describe this…