Tier 3

ape - Alphacode Pass 1 Explicit

Alphacode Pass 1 Explicit

Input: $ARGUMENTS

Overview

Pass 1 is about getting the problem RIGHT before getting clever. Explicitly decompose the problem, identify every constraint, enumerate edge cases, and implement the most straightforward correct solution. Optimization comes later.

Steps

Step 1: Parse the Problem Statement

  1. Read the entire problem statement twice
  2. Extract:
    • Input format: exact specification
    • Output format: exact specification
    • Constraints: all numerical bounds (N, M, time, memory)
    • Guarantees: what the problem promises about input
  3. Restate the problem in your own words
  4. What is the problem ACTUALLY asking? (often different from how it’s worded)

Step 2: Classify the Problem Type

  1. Core algorithmic category:
    • Graph / DP / Greedy / Math / String / Data structure / Search / Ad hoc
  2. Note if combination of types
  3. Identify the key insight being tested

Step 3: Work Through Examples

  1. Trace through EVERY provided example by hand
  2. Verify your understanding produces expected output
  3. If mismatch → problem interpretation is wrong, go back to Step 1
  4. Construct 2-3 additional small examples
  5. Look for patterns

Step 4: Identify Edge Cases

  1. Minimum input (N=1, empty, single element)
  2. Maximum input (upper constraint bounds)
  3. All-same input
  4. Sorted / reverse sorted
  5. Boundary values (0, -1, MAX_INT)
  6. Problem-specific (disconnected graph, self-loops, duplicates)
  7. Write expected output for each

Step 5: Design Algorithm

  1. Start with brute force
  2. Calculate complexity: O(?) time, O(?) space
  3. Does brute force pass? If yes → implement it. Simplicity > cleverness in Pass 1.
  4. If no → identify bottleneck, determine needed optimization
  5. State what each step does, why it’s correct, its complexity

Step 6: Implement

  1. Clean, straightforward code
  2. Descriptive variable names
  3. Handle input parsing carefully (off-by-one = #1 bug)
  4. Comment each major section

Step 7: Test

  1. Run against ALL provided examples
  2. Run against edge cases from Step 4
  3. If failure → don’t patch, understand WHY, fix root cause
  4. All pass → proceed to /api (Pass 2) if optimization needed
PASS 1 RESULT:
Problem type: [classification]
Algorithm: [description]
Complexity: O([time]) time, O([space]) space
Passes constraints: [yes/no]
Edge cases: [N of N passed]
Status: [correct / needs optimization / stuck]

When to Use

  • First attempt at any competitive programming problem
  • When you need a correct baseline before optimizing

Verification

  • Problem restated in own words
  • All constraints extracted
  • Every example traced by hand
  • Edge cases enumerated and tested
  • Correctness argued (not just tested)
  • Complexity checked against limits