# 排序數組中的最后一個重復元素 > 原文： [https://www.geeksforgeeks.org/last-duplicate-element-sorted-array/](https://www.geeksforgeeks.org/last-duplicate-element-sorted-array/) 我們有一個包含重復元素的排序數組，我們必須找到最后一個重復元素的索引并打印它的索引，還要打印重復元素。 如果找不到這樣的元素，則打印一條消息。 示例： ``` 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 ``` 我們只需以相反的順序遍歷數組，然后比較當前元素和上一個元素。 如果找到匹配項，則打印索引和重復元素。 由于這是排序數組，它將是最后一個重復項。 如果找不到此類元素，我們將為其打印消息。 ``` 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++ ```cpp // To print last duplicate element and its // index in a sorted array #include <bits/stdc++.h> 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 // 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 ```py # 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# ```cs // 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 ```php <?php // PHP 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 or $n <= 0)? ????????return; ????// compare elements and return last ????// duplicate and its index ????for ( $i = $n - 1; $i > 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\. ?> ``` **輸出**： ``` Last index: 4 Last duplicate item: 6 ``` * * * * * *