检查给定数组是否包含彼此相距 k 距离内的重复元素

给定一个可能包含重复项的未排序数组。还给出了一个小于数组大小的数字 k。编写一个函数，如果数组在 k 距离内包含重复项，则返回 true。
例子：

Input: k = 3, arr[] = {1, 2, 3, 4, 1, 2, 3, 4}
Output: false
All duplicates are more than k distance away.

Input: k = 3, arr[] = {1, 2, 3, 1, 4, 5}
Output: true
1 is repeated at distance 3.

Input: k = 3, arr[] = {1, 2, 3, 4, 5}
Output: false

Input: k = 3, arr[] = {1, 2, 3, 4, 4}
Output: true

一个简单的解决方案是运行两个循环。外循环选择每个元素 ‘arr[i]’ 作为起始元素，内循环比较所有在 ‘arr[i]’ 距离内的元素。该解决方案的时间复杂度为 O(kn)。
我们可以使用哈希在 Θ(n) 时间内解决这个问题。这个想法是通过向哈希添加元素来实现的。我们还删除了与当前元素距离超过 k 的元素。下面是详细的算法。
1) 创建一个空的哈希表。
2）从左到右遍历所有元素。让当前元素为 ‘arr[i]’
….a) 如果当前元素 ‘arr[i]’ 存在于哈希表中，则返回 true。
….b) 否则，如果 i 大于或等于 k，则将 arr[i] 添加到哈希并从哈希中删除 arr[ik]

C++

#include
using namespace std;
 
/* C++ program to Check if a given array contains duplicate
   elements within k distance from each other */
bool checkDuplicatesWithinK(int arr[], int n, int k)
{
    // Creates an empty hashset
    unordered_set myset;
 
    // Traverse the input array
    for (int i = 0; i < n; i++)
    {
        // If already present n hash, then we found
        // a duplicate within k distance
        if (myset.find(arr[i]) != myset.end())
            return true;
 
        // Add this item to hashset
        myset.insert(arr[i]);
 
        // Remove the k+1 distant item
        if (i >= k)
            myset.erase(arr[i-k]);
    }
    return false;
}
 
// Driver method to test above method
int main ()
{
    int arr[] = {10, 5, 3, 4, 3, 5, 6};
    int n = sizeof(arr) / sizeof(arr[0]);
    if (checkDuplicatesWithinK(arr, n, 3))
        cout << "Yes";
    else
        cout << "No";
}
 
//This article is contributed by Chhavi

Java

/* Java program to Check if a given array contains duplicate
   elements within k distance from each other */
import java.util.*;
 
class Main
{
    static boolean checkDuplicatesWithinK(int arr[], int k)
    {
        // Creates an empty hashset
        HashSet set = new HashSet<>();
 
        // Traverse the input array
        for (int i=0; i= k)
              set.remove(arr[i-k]);
        }
        return false;
    }
 
    // Driver method to test above method
    public static void main (String[] args)
    {
        int arr[] = {10, 5, 3, 4, 3, 5, 6};
        if (checkDuplicatesWithinK(arr, 3))
           System.out.println("Yes");
        else
           System.out.println("No");
    }
}

Python 3

# Python 3 program to Check if a given array
# contains duplicate elements within k distance
# from each other
def checkDuplicatesWithinK(arr, n, k):
 
    # Creates an empty list
    myset = []
 
    # Traverse the input array
    for i in range(n):
     
        # If already present n hash, then we
        # found a duplicate within k distance
        if arr[i] in myset:
            return True
 
        # Add this item to hashset
        myset.append(arr[i])
 
        # Remove the k+1 distant item
        if (i >= k):
            myset.remove(arr[i - k])
    return False
 
# Driver Code
if __name__ == "__main__":
     
    arr = [10, 5, 3, 4, 3, 5, 6]
    n = len(arr)
    if (checkDuplicatesWithinK(arr, n, 3)):
        print("Yes")
    else:
        print("No")
 
# This code is contributed by ita_c

C#

/* C# program to Check if a given
array contains duplicate elements
within k distance from each other */
using System;
using System.Collections.Generic;
 
class GFG
{
    static bool checkDuplicatesWithinK(int []arr, int k)
    {
        // Creates an empty hashset
        HashSet set = new HashSet();
 
        // Traverse the input array
        for (int i = 0; i < arr.Length; i++)
        {
            // If already present n hash, then we found
            // a duplicate within k distance
            if (set.Contains(arr[i]))
                return true;
 
            // Add this item to hashset
            set.Add(arr[i]);
 
            // Remove the k+1 distant item
            if (i >= k)
                set.Remove(arr[i - k]);
        }
        return false;
    }
 
    // Driver code
    public static void Main (String[] args)
    {
        int []arr = {10, 5, 3, 4, 3, 5, 6};
        if (checkDuplicatesWithinK(arr, 3))
            Console.WriteLine("Yes");
        else
            Console.WriteLine("No");
    }
}
 
// This code has been contributed
// by 29AjayKumar

Javascript

 
/* Javascript program to Check if a given array contains duplicate
   elements within k distance from each other */
    
     
    function checkDuplicatesWithinK(arr, n, k)
    {
        // Creates an empty hashset
        let myset = [];
         
        // Traverse the input array
        for(let i=0;i<n;i++)
        {
            // If already present n hash, then we found
            // a duplicate within k distance
            if(arr.includes(arr[i]))
            {
                return true;
            }
            // Add this item to hashset
            myset.add(arr[i]);
             
            // Remove the k+1 distant item
            if (i >= k)
            {
                index = array.indexOf(arr[i - k]);
                array.splice(index, 1);
            }
        }
        return false;
    }
    // Driver method to test above method
    let arr = [10, 5, 3, 4, 3, 5, 6];
    let n= arr.length;
    if (checkDuplicatesWithinK(arr, n, 3))
    {
        document.write("Yes");
    }
    else
    {
        document.write("No");
    }
     
     
    // This code is contributed by rag2127
     

输出：

Yes

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