Expense Splitter Android App

Shared expenses create a familiar mess: one person pays for dinner, another books the cab, a third covers the villa, and at the end of the trip the settlement math is argued over chat screenshots. Spreadsheets technically work, but nobody maintains one on holiday. This project implements the full expense-splitting loop as an Android app: create a group, add members, log expenses with the payer and a split mode, and watch per-member balances update live. The settlement planner answers the only question that matters — who pays whom, how much — with the minimum number of transfers, computed by a greedy creditor-debtor matching algorithm that is simple enough to explain in a viva. Recording each settlement keeps the books honest, and the activity log preserves every change.

1. The user creates a group (for example a Goa trip), adds the members, and starts logging expenses.
2. Each expense records the description, amount, who paid, and the split mode — equal, by shares, or exact amounts.
3. Per-member balances update live: what each person paid minus their share of what they owe.
4. Opening the Settle view runs the settlement planner, which matches the largest creditors with the largest debtors into a minimal transfer list.
5. Members pay each other per the plan and each payment is recorded in the app, shrinking the remaining balances.
6. The activity log keeps the full history of expenses, edits and settlements for reference or dispute resolution.

Tech stack:

• Android (Kotlin or Java) with Android SDK
• SQLite via Room for local storage
• Material Design components
• Greedy creditor-debtor settlement algorithm
• Local notifications for settlement reminders (optional)

• [Group and member management] Create groups (trips, flats, clubs), add members, and keep a separate expense ledger per group with running totals.
• [Three split modes] Split equally with one tap, by custom shares (weights) for uneven contributions, or by exact rupee amounts per member.
• [Live balances] Every member's net position — how much they are owed or owe — recomputes on every expense add, edit or delete.
• [Minimal settlement planner] A greedy creditor-debtor matching algorithm produces the smallest practical set of who-pays-whom transfers to settle the group.
• [Settlement recording] Log each payment as it happens; balances move toward zero and the plan updates for what remains.
• [Activity log] Every expense add, edit, delete and settlement is timestamped in a per-group feed for full auditability.
• [Expense history and summaries] Per-member totals, recent expenses and category views make it easy to see where the group's money went.

• Complete Android app source code (groups, expenses, settlement planner)
• Settlement-algorithm documentation with worked examples
• Sample group datasets (trip, flat, lunch club) for demonstration
• Setup guide (build, install, usage walkthrough)
• Project report PDF (background, algorithm design, methodology)
• PPT presentation for final review
• Viva Q&A preparation document (Android, SQLite, settlement algorithms)

• The settlement plan is minimal for the standard greedy-matching cases; adversarial share patterns can theoretically need more transfers — documented in the report.
• Groups are single-currency; multi-currency trips need manual conversion before entry.
• There is no payment integration — settlements are recorded manually after members pay via their own UPI or cash.
• Data lives on one device; there is no multi-user cloud sync, so all members cannot edit simultaneously.
• The app trusts entered amounts; it cannot verify that a logged expense actually happened.