When to use Monotonic Stack

Monotonic Stack helps you find the next greater or the next smaller element. It has the following characteristics.

• it is often used to solve “range queries in an array” problem
• maintain maximum and minimum elements in the range
• keep the order of elements in range
• element that have been removed never get used again

Increasing vs Decreasing

• Use increasing when you are looking for next smaller element
• Use decreasing when you are looking for next greater element

Sources

• https://medium.com/techtofreedom/algorithms-for-interview-2-monotonic-stack-462251689da8