Fractional Share Inventory Flattening
Robinhood● MediumFULLTIMEPHONE SCREENProblem statement
Robinhood can trade only whole shares with an exchange, while customers may buy or sell fractional shares. Maintain the firm's retained fractional inventory for each symbol while processing orders in order.
Every inventory row is symbol/quantity. Every order is symbol/side/quantity/currentPrice, where side is B for a customer buy or S for a customer sell. Numeric fields are fixed-point integers whose final two digits are fractional: 50 means 0.50 shares and price 1000 means $10.00. A quantity beginning with $ is a dollar amount; convert it to hundredths of a share as dollarCents * 100 / priceCents.
- A customer buy removes the requested quantity from firm inventory.
- A customer sell adds it.
- After each order, immediately buy or sell enough whole shares at the exchange that retained inventory is in
[0,100)hundredths.
Return final rows in the same symbol order and format as inventory.
Function
flattenFractionalInventory(orders: String[], inventory: String[]) → String[]Examples
Example 1
orders = ["AAPL/B/150/1000","AAPL/B/40/1000","AAPL/B/50/1000"]inventory = ["AAPL/0"]return = ["AAPL/60"]The retained inventory becomes 50, then 10, then 60 hundredths after whole-share flattening.
Example 2
orders = ["AAPL/S/75/1000","AAPL/S/50/1000","GOOGL/B/$21/100"]inventory = ["AAPL/0","GOOGL/75"]return = ["AAPL/25","GOOGL/54"]AAPL sells one accumulated whole share to the exchange. The dollar order equals 21 hundredths of GOOGL.
Constraints
1 <= inventory.length, orders.length <= 100000.- Inventory contains every ordered symbol exactly once and starts in
[0,100). - Every dollar quantity converts exactly to a whole number of hundredths of a share.
- All intermediate fixed-point values fit signed 64-bit integers.