using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;namespace Demo
{class Program{/*** 判定一个字符串中是否有重复的元素。*/static void Main(string[] args){string[] arr = new string[] { "1", "2", "3", "4", "3" };bool isContainsSameItem = IsSameWithForeach(arr);Console.WriteLine(isContainsSameItem);isContainsSameItem = IsSameWithSortAndCompare(arr);Console.WriteLine(isContainsSameItem);isContainsSameItem = IsSameWithHashSet(arr);Console.WriteLine(isContainsSameItem);isContainsSameItem = IsSameWithArrayContains(arr);Console.WriteLine(isContainsSameItem);Console.ReadKey();}/*** 利用array.contains存储及判断是否存在重复数据* **/static bool IsSameWithArrayContains(string[] arr){var newArr = new string[arr.Length];var idx = 0;foreach (var i in arr){if (false == newArr.Contains(i)){newArr[idx] = i;idx++;}else{return true;}}return false;}/*** 利用hasset的原理来实现* **/static bool IsSameWithHashSet(string[] arr){ISet<string> set = new HashSet<string>();for (var i = 0; i < arr.Length; i++){// 这里可利用该元素来实现统计重复的原理有哪些，及重复个数。//bool state = set.Add(arr[i]); // 如果返回false，表示set中已经有该元素。//Console.WriteLine(state);set.Add(arr[i]);}return set.Count != arr.Length;}/***排序后，比较相邻的数据是否有重复的。*/static bool IsSameWithSortAndCompare(string[] arr){// 先排序
            Array.Sort(arr);//Console.WriteLine(string.Join(",", arr));// 对比相邻的数据是否相同for (var i = 0; i < arr.Length - 1; i++){if (arr[i] == arr[i + 1])return true;}return false;}/*** 双层遍历*/static bool IsSameWithForeach(string[] arr){for (var i = 0; i < arr.Length - 1; i++){for (var j = i + 1; j < arr.Length; j++){if (arr[i] == arr[j])return true;}}return false;}}
}

 1             string[] arr = new string[100000];
 2             // 给arr填充为一个没有任何重复数据的数组来，测试性能。
 3             for (var i = 0; i < arr.Length; i++)
 4             {
 5                 arr[i] = i.ToString();
 6             }
 7
 8             System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
 9             watch.Start();
10             bool isContainsSameItem = IsSameWithForeach(arr);
11             Console.WriteLine(isContainsSameItem);
12             watch.Stop();
13             Console.WriteLine("IsSameWithForeach 耗时：" + watch.ElapsedMilliseconds + "milliseconds");
14
15             watch = new System.Diagnostics.Stopwatch();
16             watch.Start();
17             isContainsSameItem = IsSameWithSortAndCompare(arr);
18             Console.WriteLine(isContainsSameItem);
19             watch.Stop();
20             Console.WriteLine("IsSameWithSortAndCompare 耗时：" + watch.ElapsedMilliseconds + "milliseconds");
21
22             watch = new System.Diagnostics.Stopwatch();
23             watch.Start();
24             isContainsSameItem = IsSameWithHashSet(arr);
25             Console.WriteLine(isContainsSameItem);
26             watch.Stop();
27             Console.WriteLine("IsSameWithHashSet 耗时：" + watch.ElapsedMilliseconds + "milliseconds");
28
29             watch = new System.Diagnostics.Stopwatch();
30             watch.Start();
31             isContainsSameItem = IsSameWithArrayContains(arr);
32             Console.WriteLine(isContainsSameItem);
33             watch.Stop();
34             Console.WriteLine("IsSameWithArrayContains 耗时：" + watch.ElapsedMilliseconds + "milliseconds");
35
36             Console.ReadKey();