The Problem-Solving Process

How to attack any problem

Great programmers do not think faster — they follow a reliable process. Use this loop every time you are stuck.

The four steps

1. Understand — restate the problem in your own words; list inputs and expected outputs
2. Plan — sketch the approach, start with a brute-force idea
3. Implement — write the smallest working version
4. Reflect — test edge cases, simplify, improve speed

Worked example: find the largest number

def largest(nums):\n    if not nums:\n        return None\n    best = nums[0]\n    for n in nums[1:]:\n        if n > best:\n            best = n\n    return best

Test cases come first

assert largest([3, 9, 2, 7]) == 9\nassert largest([-5]) == -5\nassert largest([]) is None\nprint("all tests pass")

Edge cases checklist

• Empty input
• Single element
• All same values
• Negative numbers
• Very large values

When stuck

• Solve a tiny example by hand
• Draw a diagram
• Write out the brute-force version first
• Explain the problem out loud

Tip: Write the tests before the function. It forces you to understand the problem — the hardest 20% of any task.