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Stack Patterns
Overview

Stack Patterns

iedo iedo
January 16, 2026
1 min read
algorithms java stack monotonic-stack

Monotonic Decreasing Stack

import java.util.Stack;




public int fn(int[] arr) {
    Stack<Integer> stack = new Stack<>();
    int ans = 0;


    for (int num : arr) {
        while (!stack.isEmpty() && stack.peek() < num) {
            // TODO: logic
            stack.pop();
        }
        stack.push(num);
    }


    return ans;
}

Monotonic Increasing Stack

import java.util.Stack;




public int fn(int[] arr) {
    Stack<Integer> stack = new Stack<>();
    int ans = 0;


    for (int num : arr) {
        while (!stack.isEmpty() && stack.peek() > num) {
            // TODO: logic
            stack.pop();
        }
        stack.push(num);
    }


    return ans;
}