Basic Problem-Solving Using Control Flow

Control flow is what gives a program its intelligence, the ability to make decisions, repeat actions, and respond to different situations. Combining conditional statements and loops to solve real problems is a core programming skill. 

What is Control Flow in Problem-Solving?

Control flow refers to the order in which Python executes statements in a program. When solving a problem, you direct that flow using:

1. Conditionals (if, elif, else) — to make decisions

2. Loops (for, while) — to repeat actions.

3. Loop controls (break, continue, pass) — to refine loop behavior.

Good problem-solving means knowing which tool to use and when.

A Simple Approach to Solving Problems with Control Flow

Before writing any code, follow these steps:

1. Understand the problem — What is the input? What should the output be?

2. Identify the logic — Does it need a decision? A repetition? Both?

3. Choose the right control structure — Conditional, loop, or a combination.

4. Write and test the code — Start simple, then refine.

Problem 1 — Grade Classifier

Problem: Take a student's score as input and print the corresponding grade.

Logic needed: Decision-making → use if, elif, else

What this demonstrates:

1. Multiple conditions checked in order.

2. Only the first matching condition executes.

3. else handles all remaining cases.

Problem 2 — Multiplication Table Generator

Problem: Print the multiplication table of any number entered by the user.

Logic needed: Repetition → use a for loop with range().

What this demonstrates:

1. Fixed number of iterations using range().

2. f-string formatting for clean output.

3. Arithmetic inside a loop.

Problem 3 — Find the First Even Number in a List

Problem: Search through a list of numbers and stop as soon as the first even number is found.

Logic needed: Loop + condition + early exit → for + if + break

What this demonstrates:

1. Combining a loop with a condition.

2. Using break to stop once the goal is achieved.

3. Efficient searching — no unnecessary iterations.

Problem 4 — Sum of Positive Numbers Only

Problem: From a list of numbers, calculate the sum of only the positive values.

Logic needed: Loop + skip negatives → for + continue

What this demonstrates:

1. Using continue to filter out unwanted values.

2. Accumulating results inside a loop.

3. Clean separation of logic from data.

Problem 5 — User Login Attempt System

Problem: Allow a user 3 attempts to enter the correct password.

Logic needed: Repetition with condition + exit → while + break

What this demonstrates:

1. while loop for unknown repetition count.

2. break to exit on success.

3. Counter variable tracking attempts.