Solution: 100 doors

---

examples/100-doors/100_doors.go

package main

import "fmt"

func main() {
    for i, open := range doors(10) {
        fmt.Printf("%3v %v\n", i, open)
    }
}

func doors(n int) []bool {
    var doors = make([]bool, n)
    for i := 1; i <= n; i++ {
        d := i
        for d <= n {
            doors[d-1] = !doors[d-1]
            d += i
        }
    }
    return doors
}

examples/100-doors/100_doors_test.go

package main

import (
    "fmt"
    "testing"
)

func TestDoors(t *testing.T) {
    cases := make(map[int][]bool)
    cases[0] = []bool{}
    cases[1] = []bool{true}
    cases[2] = []bool{true, false}
    cases[3] = []bool{true, false, false}
    cases[4] = []bool{true, false, false, true}
    cases[5] = []bool{true, false, false, true, false}
    cases[6] = []bool{true, false, false, true, false, false}
    cases[7] = []bool{true, false, false, true, false, false, false}
    cases[8] = []bool{true, false, false, true, false, false, false, false}
    cases[9] = []bool{true, false, false, true, false, false, false, false, true}
    cases[10] = []bool{true, false, false, true, false, false, false, false, true, false}
    for i, expected := range cases {
        actual := doors(i)
        if !compare(actual, expected) {
            t.Error(fmt.Sprintf("Expected '%v', Actual '%v'", expected, actual))
        }
    }
}

func compare(a, b []bool) bool {
    //fmt.Println(a)
    //fmt.Println(b)
    if len(a) != len(b) {
        return false
    }
    for i := 0; i < len(a); i++ {
        if a[i] != b[i] {
            return false
        }
    }
    return true
}