meta.json

{
  "slug": "splitwise",
  "title": "Design Splitwise",
  "difficulty": "medium",
  "summary": "Track shared expenses across four split types where every split sums exactly to the total, keep one net balance per person instead of a debt matrix, and settle the whole group in at most n-1 payments.",
  "tags": ["fintech", "ledger", "money", "graph", "most-asked"],
  "patterns": ["strategy", "observer"],
  "concepts": [
    "Integer money, and why floats break ledgers slowly",
    "The largest remainder method for splits that do not divide evenly",
    "Net balances instead of a who-owes-whom matrix",
    "Greedy debt settlement, its n-1 bound, and why the true minimum is NP-hard",
    "Freezing derived values so history cannot be rewritten"
  ],
  "entrypoint": "src/main.py",
  "tests": "tests",
  "estimatedMinutes": 60,
  "askedAt": ["Amazon", "Uber", "Swiggy", "Razorpay", "Flipkart"],
  "diagram": { "mermaid": true },
  "extensions": [
    "Support multiple currencies and decide which exchange rate applies",
    "Add groups, and decide whether balances are per group or global",
    "Allow editing and deleting past expenses",
    "Rotate who absorbs the rounding remainder across expenses",
    "Restrict settlement suggestions to within a group",
    "Handle concurrent expense creation"
  ]
}