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Search an element in a sorted and rotated array with duplicates
• Difficulty Level : Hard
• Last Updated : 10 Jun, 2021

Given an array arr[] which is sorted and rotated, the task is to find an element in the rotated array (with duplicates) in O(log n) time.
Note: Print the index where the key exists. In case of multiple answer print any of them

Examples:

Input: arr[] = {3, 3, 3, 1, 2, 3}, key = 3
Output:
arr = 3

Input: arr[] = {3, 3, 3, 1, 2, 3}, key = 11
Output: -1
11 is not present in the given array.

Approach: The idea is the same as the previous one without duplicates. The only difference is that due to the existence of duplicates, arr[low] == arr[mid] could be possible, the first half could be out of order (i.e. not in the ascending order, e.g. {3, 1, 2, 3, 3, 3, 3}) and we have to deal this case separately.
In that case, it is guaranteed that arr[high] also equal to arr[mid], so the condition arr[mid] == arr[low] == arr[high] can be checked before the original logic, and if so then move left and right both towards the middle by 1 and repeat.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function to return the index of the``// key in arr[l..h] if the key is present``// otherwise return -1``int` `search(``int` `arr[], ``int` `l, ``int` `h, ``int` `key)``{``    ``if` `(l > h)``        ``return` `-1;` `    ``int` `mid = (l + h) / 2;``    ``if` `(arr[mid] == key)``        ``return` `mid;` `    ``// The tricky case, just update left and right``    ``if` `((arr[l] == arr[mid])``        ``&& (arr[h] == arr[mid]))``    ``{``        ``++l;``        ``--h;``        ``return` `search(arr, l, h, key);``    ``}` `    ``// If arr[l...mid] is sorted``    ``if` `(arr[l] <= arr[mid]) {` `        ``// As this subarray is sorted, we can quickly``        ``// check if key lies in any of the halves``        ``if` `(key >= arr[l] && key <= arr[mid])``            ``return` `search(arr, l, mid - 1, key);` `        ``// If key does not lie in the first half``        ``// subarray then divide the other half``        ``// into two subarrays such that we can``        ``// quickly check if key lies in the other half``        ``return` `search(arr, mid + 1, h, key);``    ``}` `    ``// If arr[l..mid] first subarray is not sorted``    ``// then arr[mid... h] must be sorted subarray``    ``if` `(key >= arr[mid] && key <= arr[h])``        ``return` `search(arr, mid + 1, h, key);` `    ``return` `search(arr, l, mid - 1, key);``}` `// Driver code``int` `main()``{``    ``int` `arr[] = { 3, 3, 1, 2, 3, 3 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(``int``);``    ``int` `key = 3;` `    ``cout << search(arr, 0, n - 1, key);` `    ``return` `0;``}`

## Java

 `// Java implementation of the approach``class` `GFG``{``    ` `    ``// Function to return the index of the``    ``// key in arr[l..h] if the key is present``    ``// otherwise return -1``    ``static` `int` `search(``int` `arr[], ``int` `l, ``int` `h, ``int` `key)``    ``{``        ``if` `(l > h)``            ``return` `-``1``;``    ` `        ``int` `mid = (l + h) / ``2``;``        ``if` `(arr[mid] == key)``            ``return` `mid;``    ` `        ``// The tricky case, just update left and right``        ``if` `((arr[l] == arr[mid])``            ``&& (arr[h] == arr[mid]))``        ``{``            ``l++;``            ``h--;``              ``return` `search(arr,l,h,key);``        ``}``    ` `        ``// If arr[l...mid] is sorted``        ``else` `if` `(arr[l] <= arr[mid])``        ``{``    ` `            ``// As this subarray is sorted, we can quickly``            ``// check if key lies in any of the halves``            ``if` `(key >= arr[l] && key <= arr[mid])``                ``return` `search(arr, l, mid - ``1``, key);``    ` `            ``// If key does not lie in the first half``            ``// subarray then divide the other half``            ``// into two subarrays such that we can``            ``// quickly check if key lies in the other half``            ``else``              ``return` `search(arr, mid + ``1``, h, key);``        ``}``    ` `        ``// If arr[l..mid] first subarray is not sorted``        ``// then arr[mid... h] must be sorted subarray``           ``else`  `if` `(key >= arr[mid] && key <= arr[h])``            ``return` `search(arr, mid + ``1``, h, key);``    ` `        ``return` `search(arr, l, mid - ``1``, key);``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `arr[] ={``3``, ``3``, ``1``, ``2``, ``3``, ``3``};``        ``int` `n = arr.length;``        ``int` `key = ``3``;``    ` `        ``System.out.println(search(arr, ``0``, n - ``1``, key));``    ``}``}` `// This code is contributed by AnkitRai01`

## Python3

 `# Python3 implementation of the approach` `# Function to return the index of the``# key in arr[l..h] if the key is present``# otherwise return -1``def` `search(arr, l, h, key) :` `    ``if` `(l > h) :``        ``return` `-``1``;``        ` `    ``mid ``=` `(l ``+` `h) ``/``/` `2``;``    ``if` `(arr[mid] ``=``=` `key) :``        ``return` `mid;` `    ``# The tricky case, just update left and right``    ``if` `((arr[l] ``=``=` `arr[mid]) ``and` `(arr[h] ``=``=` `arr[mid])) :``        ``l ``+``=` `1``;``        ``h ``-``=` `1``;``        ``return` `search(arr, l, h, key)``    ``# If arr[l...mid] is sorted``    ``if` `(arr[l] <``=` `arr[mid]) :` `        ``# As this subarray is sorted, we can quickly``        ``# check if key lies in any of the halves``        ``if` `(key >``=` `arr[l] ``and` `key <``=` `arr[mid]) :``            ``return` `search(arr, l, mid ``-` `1``, key);` `        ``# If key does not lie in the first half``        ``# subarray then divide the other half``        ``# into two subarrays such that we can``        ``# quickly check if key lies in the other half``        ``return` `search(arr, mid ``+` `1``, h, key);` `    ``# If arr[l..mid] first subarray is not sorted``    ``# then arr[mid... h] must be sorted subarray``    ``if` `(key >``=` `arr[mid] ``and` `key <``=` `arr[h]) :``        ``return` `search(arr, mid ``+` `1``, h, key);` `    ``return` `search(arr, l, mid ``-` `1``, key);` `# Driver code``if` `__name__ ``=``=` `"__main__"` `:` `    ``arr ``=` `[ ``3``, ``3``, ``1``, ``2``, ``3``, ``3` `];``    ``n ``=` `len``(arr);``    ``key ``=` `3``;` `    ``print``(search(arr, ``0``, n ``-` `1``, key));` `# This code is contributed by AnkitRai01`

## C#

 `// C# implementation of the approach``using` `System;` `class` `GFG``{``    ` `    ``// Function to return the index of the``    ``// key in arr[l..h] if the key is present``    ``// otherwise return -1``    ``static` `int` `search(``int` `[]arr, ``int` `l, ``int` `h, ``int` `key)``    ``{``        ``if` `(l > h)``            ``return` `-1;``    ` `        ``int` `mid = (l + h) / 2;``        ``if` `(arr[mid] == key)``            ``return` `mid;``    ` `        ``// The tricky case, just update left and right``        ``if` `((arr[l] == arr[mid])``            ``&& (arr[h] == arr[mid]))``        ``{``            ``++l;``            ``--h;``            ``return` `search(arr, l, h, key)``        ``}``    ` `        ``// If arr[l...mid] is sorted``        ``if` `(arr[l] <= arr[mid])``        ``{``    ` `            ``// As this subarray is sorted, we can quickly``            ``// check if key lies in any of the halves``            ``if` `(key >= arr[l] && key <= arr[mid])``                ``return` `search(arr, l, mid - 1, key);``    ` `            ``// If key does not lie in the first half``            ``// subarray then divide the other half``            ``// into two subarrays such that we can``            ``// quickly check if key lies in the other half``            ``return` `search(arr, mid + 1, h, key);``        ``}``    ` `        ``// If arr[l..mid] first subarray is not sorted``        ``// then arr[mid... h] must be sorted subarray``        ``if` `(key >= arr[mid] && key <= arr[h])``            ``return` `search(arr, mid + 1, h, key);``    ` `        ``return` `search(arr, l, mid - 1, key);``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `Main ()``    ``{``        ``int` `[]arr = { 3, 3, 1, 2, 3, 3 };``        ``int` `n = arr.Length;``        ``int` `key = 3;``    ` `        ``Console.WriteLine(search(arr, 0, n - 1, key));``    ``}``}` `// This code is contributed by AnkitRai01`

## Javascript

 ``
Output
`4`

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