Serve the pickup line

EasyArraysQueues

Customers join a pickup line and are served in arrival order. Read events from left to right. A positive integer joins the back of the line with that ticket number. A zero asks the counter to serve the oldest waiting ticket. Return one number for every zero: the ticket served, or -1 if the line was empty. Repeated ticket numbers represent separate arrivals. Tickets still waiting after the last event do not appear in the answer.

Example 1

INPUT[8,3,0,5,0,0]OUTPUT[8,3,5]

Ticket 8 arrived first, followed by 3 and then 5. Each zero serves the oldest waiting ticket.

Example 2

INPUT[0,4,0,0]OUTPUT[-1,4,-1]

The line is empty for the first and last service commands. Ticket 4 is served by the middle one.

Keep in mind

0 <= events.length <= 20,000
Each event is an integer from 0 to 1,000,000.
Zero is a service command, never a ticket number.

/** @returns {number[]} */
function solve(events) {
  // Return the result described above.
}

/** @returns {number[]} */
function solve(events) {
  // Return the result described above.
}

INPUT[8,3,0,5,0,0]

EXPECTED OUTPUT[8,3,5]

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Serve the pickup line

Example 1

Example 2

Keep in mind

How the solution works.

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