linq-Intersect

源码：

        public static IEnumerable<TSource> Intersect<TSource>(this IEnumerable<TSource> first, IEnumerable<TSource> second) {
            if (first == null) throw Error.ArgumentNull("first");
            if (second == null) throw Error.ArgumentNull("second");
            return IntersectIterator<TSource>(first, second, null);
        }
 
        public static IEnumerable<TSource> Intersect<TSource>(this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
        {
            if (first == null) throw Error.ArgumentNull("first");
            if (second == null) throw Error.ArgumentNull("second");
            return IntersectIterator<TSource>(first, second, comparer);
        }
 
        static IEnumerable<TSource> IntersectIterator<TSource>(IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer)
        {
            Set<TSource> set = new Set<TSource>(comparer);
            foreach (TSource element in second) set.Add(element);
            foreach (TSource element in first)
                if (set.Remove(element)) yield return element;
        }

        // If value is in set, remove it and return true; otherwise return false
        public bool Remove(TElement value) {
            int hashCode = InternalGetHashCode(value);
            int bucket = hashCode % buckets.Length;
            int last = -1;
            for (int i = buckets[bucket] - 1; i >= 0; last = i, i = slots[i].next) {
                if (slots[i].hashCode == hashCode && comparer.Equals(slots[i].value, value)) {
                    if (last < 0) {
                        buckets[bucket] = slots[i].next + 1;
                    }
                    else {
                        slots[last].next = slots[i].next;
                    }
                    slots[i].hashCode = -1;
                    slots[i].value = default(TElement);
                    slots[i].next = freeList;
                    freeList = i;
                    return true;
                }
            }
            return false;
        }

这个是用来去重的。源码可以去分析下。