🧩intermediate

Breaking Problems into Steps — Decomposition

Master decomposition, the most important skill in programming: breaking complex problems into small, solvable pieces.

Big Problems are Just Small Problems Stacked Up

How do you eat an elephant? One bite at a time. (Not a real elephant — it is just a saying!) Decomposition means breaking a big, scary problem into smaller problems that are each easy to solve. It is the single most important skill in programming. Building a social media app sounds impossible. But break it down: - Make a login page (doable!) - Make a form to create a post (doable!) - Display a list of posts (doable!) - Add a like button to posts (doable!) Suddenly each piece is something you could actually build. Decomposition turns the impossible into a checklist.

How to Decompose a Problem

Follow these steps: 1. Define the BIG problem clearly 'Build a quiz app for studying' 2. List the MAIN parts - Question display - Answer input - Score tracking - Results screen 3. Break each part into SMALLER steps Score tracking: - Start score at 0 - Add 1 point for correct answers - Display current score - Show final score at end 4. Break down AGAIN if any step still feels big Keep going until every step is something you could code in 15-30 minutes. That is your to-do list!

Decomposition Example: Building a To-Do App

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BIG PROBLEM: Build a to-do list app

Part 1: Display tasks
  - Create an empty list to store tasks
  - Show each task as a list item on screen
  - Show 'No tasks yet' if list is empty

Part 2: Add tasks
  - Create an input field and Add button
  - When button clicked, read the input
  - Add input text to the task list
  - Clear the input field
  - Refresh the display

Part 3: Complete tasks
  - Add a checkbox to each task
  - When checked, mark task as done
  - Show completed tasks with strikethrough

Part 4: Delete tasks
  - Add a delete button to each task
  - When clicked, remove task from list
  - Refresh the display

Now each step is small and buildable!

Pro Tip

Professional developers use this technique every single day. In team settings, they break projects into 'tickets' or 'stories' — small, well-defined pieces of work. A ticket might say: 'Add a delete button to task items that removes the task when clicked.' That is specific enough that any developer on the team could pick it up and build it.

Decompose a Real Project

Pick one of these projects and break it into the smallest possible steps: A) A weather app that shows the current temperature for any city. B) A flashcard app for studying vocabulary. C) A personal diary/journal app. For your chosen project, write out: the main parts (at least 4), the smaller steps within each part (at least 3 per part), and the order you would build them in (start with the most important feature). If any step takes more than a sentence to describe, break it down further!

Pseudocode & Flowcharts — Planning Your Code

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