PREVIOUS GREATER ELEMENT IN ARRAY USING STACK IN JAVA | BHARAT TECH SHOW
Learn how to efficiently find the Previous Greater Element (PGE) in an array using Stack in Java. This tutorial is perfect for beginners, DSA learners, and anyone preparing for coding interviews.
What you will learn in this video:
🔹 Definition of Previous Greater Element (PGE):
The nearest element on the left of a given element in the array that is greater than the current element.
If no such element exists, we consider it as -1.
🔹 Importance of PGE in DSA:
Used in solving problems related to stock span, histogram area, and other array-based problems.
Helps improve understanding of stack-based problem solving.
🔹 Why use Stack for this problem:
Stack allows us to efficiently keep track of potential greater elements.
Reduces time complexity from O(n²) in brute force to O(n).
🔹 Step-by-step Java Implementation:
Create a stack to store elements.
Traverse the array from left to right.
For each element:
Pop elements from the stack until we find a greater element.
If stack is empty, assign -1 as PGE.
Push the current element onto the stack.
Print the PGE array after computation.
🔹 Dry Run and Example Explained:
Example array given and each step visualized.
Helps in understanding how stack operations work for this problem.
🔹 Who this video is for:
Beginners learning Java and DSA.
Students preparing for coding interviews.
Anyone who wants to understand stack-based array problems in depth.
Bharat Tech Show – Learn Java, DSA, and Programming with step-by-step tutorials and easy explanations.
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