RabbitsinForest.go

func numRabbits(answers []int) int {
    if len(answers) == 0 {
        return 0
    }
    
    cnt := make(map[int]int)
    sum := 0
    
    for _, n := range answers {
        cnt[n]++
    }
    
    for k := range cnt {
        for cnt[k] > 0 {
            if k == 0 {
                sum += cnt[k]
                break
            } else {
                sum = sum + k + 1
                cnt[k] = cnt[k] - k - 1
            }
        }
    }
    return sum
}