c#集合去重&排序常用方法

 list与数组转Hashset&SortedSet

//创建hashset去重
var hashSet = new HashSet<int>(){1,1,2,2};
Console.WriteLine("HashSet:"+String.Join(", ", hashSet));
// HashSet:1, 2

//创建list包含重复元素
var ints = new List<int>{1,1,3,3,2,2};
//创建数组转HashSe包含重复元素
int[] numbers = { 1, 1, 3, 2, 2 };


//list转HashSet
var set = ints.ToHashSet();
Console.WriteLine("List转HashSet:"+String.Join(", ", set));
//List转HashSet:1, 3, 2

var immutableSortedSet = ints.ToImmutableSortedSet();
Console.WriteLine("immutableSortedSet:"+String.Join(", ", immutableSortedSet));


//数组转HashSet
var hashSet1 = new HashSet<int>(numbers);
Console.WriteLine("数组转HashSet:"+String.Join(", ", hashSet1));
//数组转HashSet:1, 3, 2

//数组转SortedSet
var sortedSet = new SortedSet<int>(numbers);
Console.WriteLine("数组转SortedSet:"+String.Join(", ", sortedSet));
//数组转SortedSet:1, 2, 3

当hashset存的是类时

创建饮料类

public class Drink
{
    public String Name { get; set; }
    
    public int Price { get; set; }
}

new一个HashSet存放饮料类 

var drinks = new HashSet<Drink>();
drinks.Add(new Drink{Name = "牛奶",Price = 19});
drinks.Add(new Drink{Name = "牛奶",Price = 20});
drinks.Add(new Drink{Name = "茉莉花茶",Price = 19});
drinks.Add(new Drink{Name = "茉莉花茶",Price = 19});
foreach (var drink in drinks)
{
    Console.WriteLine(drink.Name+drink.Price);
}

 打印出来并未去重

自定义比较规则

public class DrinkEquelityCompare : IEqualityComparer<Drink>
{
    public bool Equals(Drink x, Drink y)
    {
        //Name相等去除
        return x.Name == y.Name;
    }

    public int GetHashCode(Drink obj)
    {
        return base.GetHashCode();
    }
}

重新new一个类

//var drinks = new HashSet<Drink>(new DrinkEquelityCompare());
drinks.Add(new Drink{Name = "牛奶",Price = 19});
drinks.Add(new Drink{Name = "牛奶",Price = 20});
drinks.Add(new Drink{Name = "茉莉花茶",Price = 19});
drinks.Add(new Drink{Name = "茉莉花茶",Price = 19});
foreach (var drink in drinks)
{
    Console.WriteLine(drink.Name+drink.Price);
}

此时打印以及去除掉Name相同的值了

 SortedSet存放类时自定义排序规则

 还是用刚刚的Drink类

public class DrinkCompare : IComparer<Drink>
{
    public int Compare(Drink x, Drink y)
    {
        //返回值>0 x大；  返回值=0，一样大；  返回值小于0，y大
        return x.Price-y.Price;
    }
}

添加数据

SortedSet<Drink> sorted = new(new DrinkCompare());
sorted.Add(new Drink{Name = "橘汁",Price = 19});
sorted.Add(new Drink{Name = "牛奶",Price = 20});
sorted.Add(new Drink{Name = "茉莉花茶",Price = 17});
sorted.Add(new Drink{Name = "可乐",Price = 21});

foreach (var drink in sorted)
{
    Console.WriteLine(drink.Name+drink.Price);
}

打印出来的数据以及按照price进行排序了