排序数组中的最后一个重复元素

我们有一个包含重复元素的排序数组，我们必须找到最后一个重复元素的索引并打印它的索引，还要打印重复元素。如果找不到这样的元素，则打印一条消息。
例子：

Input : arr[] = {1, 5, 5, 6, 6, 7}
Output :
Last index: 4
Last duplicate item: 6

Input : arr[] = {1, 2, 3, 4, 5}
Output : No duplicate found

我们只需要以相反的顺序遍历数组，然后比较当前元素和上一个元素。如果找到匹配项，则打印索引和重复元素。由于这是排序数组，因此它将是最后一个重复项。如果找不到这样的元素，我们将为其打印消息。

1- for i = n-1 to 0
     if (arr[i] == arr[i-1])
        Print current element and its index.
        Return
2- If no such element found print a message 
   of no duplicate found.

C++

// To print last duplicate element and its
// index in a sorted array
#include 
 
void dupLastIndex(int arr[], int n) {
 
  // if array is null or size is less
  // than equal to 0 return
  if (arr == NULL || n <= 0)
    return;
   
  // compare elements and return last
  // duplicate and its index
  for (int i = n - 1; i > 0; i--) {
    if (arr[i] == arr[i - 1]) {
      printf("Last index: %d\nLast "
            "duplicate item: %d\n", i, arr[i]);
      return;
    }
  }
 
  // If we reach here, then no duplicate
  // found.
  printf("no duplicate found");
}
 
int main() {
  int arr[] = {1, 5, 5, 6, 6, 7, 9};
  int n = sizeof(arr) / sizeof(int);
  dupLastIndex(arr, n);
  return 0;
}

Java

// Java code to print last duplicate element
// and its index in a sorted array
import java.io.*;
 
class GFG
{
    static void dupLastIndex(int arr[], int n)
    {
        // if array is null or size is less
        // than equal to 0 return
        if (arr == null || n <= 0)
            return;
         
        // compare elements and return last
        // duplicate and its index
        for (int i = n - 1; i > 0; i--)
        {
            if (arr[i] == arr[i - 1])
            {
            System.out.println("Last index:" + i);
            System.out.println("Last duplicate item: "
                              + arr[i]);
            return;
            }
        }
         
        // If we reach here, then no duplicate
        // found.
        System.out.print("no duplicate found");
    }
 
    // Driver code
    public static void main (String[] args)
    {
        int arr[] = {1, 5, 5, 6, 6, 7, 9};
        int n = arr.length;
        dupLastIndex(arr, n);
         
    }
}
 
// This code is contributed by vt_m

Python3

# Python3 code to print last duplicate
# element and its index in a sorted array
 
def dupLastIndex(arr, n):
 
    # if array is null or size is less
    # than equal to 0 return
    if (arr == None or n <= 0):
        return
 
    # compare elements and return last
    # duplicate and its index
    for i in range(n - 1, 0, -1):
         
        if (arr[i] == arr[i - 1]):
            print("Last index:", i, "\nLast",
                     "duplicate item:",arr[i])
            return
         
    # If we reach here, then no duplicate
    # found.
    print("no duplicate found")
     
 
arr = [1, 5, 5, 6, 6, 7, 9]
n = len(arr)
dupLastIndex(arr, n)
 
# This code is contributed by
# Smitha Dinesh Semwal

C#

// C# code to print last duplicate element
// and its index in a sorted array
using System;
 
class GFG {
     
    static void dupLastIndex(int []arr, int n)
    {
         
        // if array is null or size is less
        // than equal to 0 return
        if (arr == null || n <= 0)
            return;
         
        // compare elements and return last
        // duplicate and its index
        for (int i = n - 1; i > 0; i--)
        {
            if (arr[i] == arr[i - 1])
            {
                Console.WriteLine("Last index:" + i);
                Console.WriteLine("Last duplicate item: "
                                + arr[i]);
                return;
            }
        }
         
        // If we reach here, then no duplicate
        // found.
        Console.WriteLine("no duplicate found");
    }
 
    // Driver code
    public static void Main ()
    {
        int []arr = {1, 5, 5, 6, 6, 7, 9};
        int n = arr.Length;
         
        dupLastIndex(arr, n);
    }
}
 
// This code is contributed by vt_m.

PHP

 0; $i--)
    {
        if ($arr[$i] == $arr[$i - 1])
        {
            echo "Last index:", $i , "\n";
            echo "Last duplicate item:", $arr[$i];
            return;
    }
}
 
    // If we reach here, then
    // no duplicate found.
    echo "no duplicate found";
}
 
// Driver Code
$arr = array(1, 5, 5, 6, 6, 7, 9);
$n = count($arr);
dupLastIndex($arr, $n);
 
// This code is contributed by anuj_67.
?>

Javascript

 
// JavaScript program to print last duplicate element
// and its index in a sorted array
 
    function dupLastIndex(arr, n)
    {
        // if array is null or size is less
        // than equal to 0 return
        if (arr == null || n <= 0)
            return;
           
        // compare elements and return last
        // duplicate and its index
        for (let i = n - 1; i > 0; i--)
        {
            if (arr[i] == arr[i - 1])
            {
            document.write("Last index:" + i + "<br/>");
            document.write("Last duplicate item: "
                              + arr[i] + "<br/>");
            return;
            }
        }
           
        // If we reach here, then no duplicate
        // found.
        document.write("no duplicate found");
    }
 
  
// Driver code
 
        let arr = [1, 5, 5, 6, 6, 7, 9];
        let n = arr.length;
        dupLastIndex(arr, n);
 

输出：

Last index: 4
Last duplicate item: 6