unmatch.go

package piscine

func Unmatch(arr []int) int {
	result := 4
	for i := range arr {
		if !ispair(arr[i], i, arr) {
			result = arr[i]
			return result
		}
	}
	return result
}

func ispair(elt, index int, arr []int) bool {
	for i := range arr {
		if i != index {
			if arr[i] == elt {
				return true
			}
		}
	}
	return false
}