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5.Problem Solving Strategies

Develop a systematic approach to solving programming problems and debugging your code.

35 minutes
Intermediate
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The Problem Solving Framework

Effective problem solving follows a structured approach. Here's a framework that works for most programming problems.

The 5-Step Process

  1. Understand the Problem: Read carefully, identify inputs/outputs, clarify requirements
  2. Plan Your Approach: Break down the problem, choose algorithms/data structures
  3. Write the Code: Implement your solution step by step
  4. Test Your Solution: Check with examples, edge cases, and different inputs
  5. Optimize: Look for ways to improve efficiency or readability

Example: Reverse a String

Let's apply this framework to reverse a string:

1. Understand

Input: "hello" → Output: "olleh"

We need to take a string and return it backwards.

2. Plan

  • Start from the end of the string
  • Build a new string character by character
  • Or use built-in reverse methods

3. Implement

def reverse_string(s):
    return s[::-1]  # Python slice notation

# Alternative approach
def reverse_string_manual(s):
    result = ""
    for i in range(len(s) - 1, -1, -1):
        result += s[i]
    return result

4. Test

print(reverse_string("hello"))  # "olleh"
print(reverse_string(""))       # ""
print(reverse_string("a"))      # "a"
print(reverse_string("123"))    # "321"

5. Optimize

The slice approach is already optimal for Python. The manual approach could be improved using a list and join.

Common Problem Types

Here are some common types of programming problems:

Array/String Problems

  • Finding elements (search, filter)
  • Modifying elements (sort, reverse, transform)
  • Counting elements
  • Finding patterns

Mathematical Problems

  • Number operations
  • Prime numbers
  • Factorials
  • Fibonacci sequence

Logic Problems

  • Conditional statements
  • Boolean logic
  • Decision trees

Practice Problem

Try solving this problem using the 5-step framework:

🎯 Challenge

Write a function that counts the number of vowels in a string. Vowels are a, e, i, o, u (both uppercase and lowercase).

Example: count_vowels("Hello World") should return 3.

Solution

def count_vowels(s):
    vowels = "aeiouAEIOU"
    count = 0
    for char in s:
        if char in vowels:
            count += 1
    return count

# Test
print(count_vowels("Hello World"))  # 3
print(count_vowels("Python"))       # 1
print(count_vowels("AEIOU"))        # 5

Tips for Success

  • Start with simple examples
  • Draw diagrams or write pseudocode
  • Test with edge cases (empty input, single element, etc.)
  • Don't be afraid to start with a simple solution and improve it
  • Practice regularly with different types of problems
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