check cardinality before check subset

Author: nextzhou

threadunsafe.go

@@ -76,6 +76,9 @@ func (set *threadUnsafeSet) Contains(i ...interface{}) bool {
 
 func (set *threadUnsafeSet) IsSubset(other Set) bool {
 	_ = other.(*threadUnsafeSet)
+	if set.Cardinality() > other.Cardinality() {
+		return false
+	}
 	for elem := range *set {
 		if !other.Contains(elem) {
 			return false