Ledger Lookup

easy

An accountant keeps invoice numbers in a ledger sorted ascending, no duplicates. Given the sorted list ledger and an invoice number invoice, return the index where it appears — or -1 if it was never filed.

Your lookup must run in O(log n): the ledger is long and the accountant is impatient.

Example 1

in ledger = [-1, 0, 3, 5, 9, 12], invoice = 9

out 4

Example 2

in ledger = [-1, 0, 3, 5, 9, 12], invoice = 2

out -1

Constraints

· 1 <= len(ledger) <= 2000
· -10^4 <= ledger[i], invoice <= 10^4
· ledger is strictly increasing