Tailor Swift Ticket Sales Counter

swifty.go

package swifty

// CountTicketSales will return how many tickets will be sold by the time the
// line pos has obtained all of their tickets. Tickets must be sold one at a
// time, and people have to return to the back of the line in order to buy their
// ticket.
func CountTicketSales(line []int, pos int) int {
	if len(line) == 0 {
		return 0
	}

	var sales int
	var newLine []int

	for idx, tickets := range line {
		if tickets > 0 {
			sales++
		}

		tickets--

		if tickets <= 0 {
			if pos == idx {
				return sales
			}
		}

		newLine = append(newLine, tickets)
	}

	return CountTicketSales(newLine, pos) + sales
}

// CountTicketSalesOptimized is a optimized version of the CountTicketSales
// initial implementation that deals with longer lines in a more efficient, and
// less time consuming way.
func CountTicketSalesOptimized(line []int, pos int) int {
	if len(line) == 0 {
		return 0
	}

	var newLine []int
	var sales int

	for idx, tickets := range line {
		if tickets > 0 {
			sales++
		}

		tickets--

		if tickets <= 0 {
			if pos == idx {
				return sales
			} else if idx > pos {
				pos--
			}
		}

		if tickets > 0 {
			newLine = append(newLine, tickets)
		}
	}

	return CountTicketSalesOptimized(newLine, pos) + sales
}

swifty_test.go

package swifty

import (
	"testing"
)

var ticketSalesTests = []struct {
	in  []int
	pos int
	out int
}{
	{in: []int{}, pos: 2, out: 0},
	{in: []int{3, 2, 5}, pos: 1, out: 5},
	{in: []int{3, 1}, pos: 1, out: 2},
	{in: []int{1, 3, 1}, pos: 1, out: 5},
}

func TestCountTicketSales(t *testing.T) {
	for _, tt := range ticketSalesTests {
		c := CountTicketSales(tt.in, tt.pos)
		if c != tt.out {
			t.Errorf("%v got %d, want %d", tt.in, c, tt.out)
		}
	}
}

func TestCountTicketSalesOptimized(t *testing.T) {
	for _, tt := range ticketSalesTests {
		c := CountTicketSalesOptimized(tt.in, tt.pos)
		if c != tt.out {
			t.Errorf("%v got %d, want %d", tt.in, c, tt.out)
		}
	}
}

func BenchmarkCountTicketSales(b *testing.B) {
	for n := 0; n < b.N; n++ {
		vals := ticketSalesTests[len(ticketSalesTests)-1]
		CountTicketSales(vals.in, vals.pos)
	}
}

func BenchmarkCountTicketSalesOptimized(b *testing.B) {
	for n := 0; n < b.N; n++ {
		vals := ticketSalesTests[len(ticketSalesTests)-1]
		CountTicketSalesOptimized(vals.in, vals.pos)
	}
}