Concurrent bank transfers without deadlock

EdgeCampus keeps a "compute credit" account per research group. Transfers run concurrently on a thread pool; each transfer must lock both accounts, and must never deadlock.

Input: first line nAccounts nThreads; second line the initial balances of accounts 0…nAccounts−1; then transfers from to amount until the end of input (overdrafts are allowed; from ≠ to).

Requirements:

• Use one ReentrantLock per account and an ExecutorService with nThreads threads; submit one task per transfer.
• Each task locks the two accounts in increasing account number order (to prevent deadlock), moves the amount, unlocks in finally.
• Wait for all tasks (shutdown + awaitTermination), then print account i: balance for every account, Total before: X, Total after: Y and Conservation: OK if equal, else Conservation: BROKEN, and Transfers: n.

Because every transfer is applied exactly once and addition is commutative, the final balances are deterministic even though the order of execution is not.

Input:

3 4
100 50 0
0 1 30
1 2 20
2 0 5
1 0 10

Output:

account 0: 85
account 1: 50
account 2: 15
Total before: 150
Total after: 150
Conservation: OK
Transfers: 4