{"id":25266,"date":"2017-10-15T16:29:37","date_gmt":"2017-10-15T10:59:37","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=25266"},"modified":"2017-10-15T16:29:37","modified_gmt":"2017-10-15T10:59:37","slug":"search-almost-sorted-array","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/search-almost-sorted-array\/","title":{"rendered":"Search in an almost sorted array"},"content":{"rendered":"

Given an array which is sorted, but after sorting some elements are moved to either of the adjacent positions, i.e., arr[i] may be present at arr[i+1] or arr[i-1]. Write an efficient function to search an element in this array<\/span>. Basically the element arr[i] can only be swapped with either arr[i+1] or arr[i-1].<\/p>\n

For example consider the array {2, 3, 10, 4, 40}, 4 is moved to next position and 10 is moved to previous position.<\/p>\n

Example:<\/p>\n

Input: arr[] =  {10, 3, 40, 20, 50, 80, 70}, key = 40\r\nOutput: 2 \r\nOutput is index of 40 in given array\r\n\r\nInput: arr[] =  {10, 3, 40, 20, 50, 80, 70}, key = 90\r\nOutput: -1\r\n-1 is returned to indicate element is not present<\/pre>\n
A simple solution is to linearly search the given key in given array. Time complexity of this solution is O(n). We cab modify binary search<\/a> to do it in O(Logn) time.<\/p>\n[ad type=”banner”]\n
The idea is to compare the key with middle 3 elements, if present then return the index. If not present, then compare the key with middle element to decide whether to go in left half or right half. Comparing with middle element is enough as all the elements after mid+2 must be greater than element mid and all elements before mid-2 must be smaller than mid element.<\/p>\n
Following is C++ implementation of this approach.<\/p>\n
C++<\/strong><\/p>\n
 
 c++<\/span> <\/div> 
\/\/ C++ program to find an element in an almost sorted\/\/ array#include <stdio.h> \/\/ A recursive binary search based function. It returns\/\/ index of x in given array arr[l..r] is present, \/\/ otherwise -1int binarySearch(int arr[], int l, int r, int x){   if (r >= l)   {        int mid = l + (r - l)\/2;         \/\/ If the element is present at one of the middle         \/\/ 3 positions        if (arr[mid] == x)  return mid;        if (mid > l && arr[mid-1] == x) return (mid - 1);        if (mid < r && arr[mid+1] == x) return (mid + 1);         \/\/ If element is smaller than mid, then it can only         \/\/ be present in left subarray        if (arr[mid] > x) return binarySearch(arr, l, mid-2, x);         \/\/ Else the element can only be present in right subarray        return binarySearch(arr, mid+2, r, x);   }    \/\/ We reach here when element is not present in array   return -1;} \/\/ Driver program to test above functionint main(void){   int arr[] = {3, 2, 10, 4, 40};   int n = sizeof(arr)\/ sizeof(arr[0]);   int x = 4;   int result = binarySearch(arr, 0, n-1, x);   (result == -1)? printf("Element is not present in array")                 : printf("Element is present at index %d", result);   return 0;}<\/code><\/pre> <\/div>\n
JAVA<\/strong><\/p>\n
 
 JAVA<\/span> <\/div> 
\/\/ Java program to find an element in an almost sorted arrayclass SearchAlmost{    \/\/ A recursive binary search based function. It returns    \/\/ index of x in given array arr[l..r] is present,    \/\/ otherwise -1    int binarySearch(int arr[], int l, int r, int x)    {        if (r >= l)        {            int mid = l + (r - l)\/2;             \/\/ If the element is present at one of the middle            \/\/ 3 positions            if (arr[mid] == x)  return mid;            if (mid > l && arr[mid-1] == x) return (mid - 1);            if (mid < r && arr[mid+1] == x) return (mid + 1);             \/\/ If element is smaller than mid, then it can            \/\/ only be present in left subarray            if (arr[mid] > x) return binarySearch(arr, l, mid-2, x);             \/\/ Else the element can only be present in right            \/\/ subarray            return binarySearch(arr, mid+2, r, x);        }         \/\/ We reach here when element is not present in array        return -1;    }     \/\/ Driver method    public static void main(String args[])    {        abc ob = new abc();        int arr[] = {3, 2, 10, 4, 40};        int n = arr.length;        int x = 4;        int result = ob.binarySearch(arr, 0, n-1, x);        if(result == -1)            System.out.println("Element is not present in array");        else            System.out.println("Element is present at index " +                               result);    }}<\/code><\/pre> <\/div>\n
Output:<\/p>\n
Element is present at index 3<\/pre>\n
Time complexity of the above function is O(Logn).<\/p>\n[ad type=”banner”]\n
 <\/p>\n","protected":false},"excerpt":{"rendered":"
Search in an almost sorted array – Searching and Sorting – A simple solution is linearly search given key in given array.Time complexity of solution is O(n).We cab modify binary search to do it in O(Logn) time.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[69969,71670,83512],"tags":[71128,71222,72388,71133,71893,72390,72302,70892,71121,71135,71134,71141,71131,71130,72305,72392,72389,71144,70895,70017,72386,71160,71158,70969,70075,70914,70046,71714,71265,70272,72695,70016,70548,72387,72385,72299,71695,70020,71161,72391,71149,72384,70967,72303,71156,71219,71142,72190,72185],"class_list":["post-25266","post","type-post","status-publish","format-standard","hentry","category-algorithm","category-searching-and-sorting","category-sorted-array","tag-algorithm-for-bubble-sort","tag-algorithm-for-insertion-sort","tag-algorithm-for-sorting","tag-algorithm-of-bubble-sort","tag-algorithm-sort","tag-array-sorting-algorithm","tag-best-sorting","tag-best-sorting-algorithm","tag-bubble-sort-algorithm","tag-bubble-sort-algorithm-in-data-structure","tag-bubble-sort-algorithm-with-example","tag-bubble-sort-animation","tag-bubble-sort-code","tag-bubble-sort-in-data-structure","tag-c-sort","tag-c-sorting-algorithms","tag-common-sorting-algorithms","tag-different-sorting-algorithms","tag-fastest-sorting-algorithm","tag-insertion-sort-algorithm","tag-insertion-sort-animation","tag-insertion-sort-in-data-structure","tag-java-sort","tag-java-sorting-algorithms","tag-linear-sort","tag-most-efficient-sorting-algorithm","tag-quicksort","tag-quicksort-algorithm-in-data-structure","tag-quicksort-example","tag-search-algorithms","tag-search-in-an-almost-sorted-array","tag-selection-sort-algorithm","tag-selection-sort-in-data-structure","tag-simple-sorting-algorithm","tag-sort-algorithm-c","tag-sort-c","tag-sorted","tag-sorting-algorithms","tag-sorting-algorithms-comparison","tag-sorting-algorithms-examples","tag-sorting-algorithms-in-data-structures","tag-sorting-algorithms-in-data-structures-with-examples","tag-sorting-algorithms-java","tag-sorting-algorithms-visualized","tag-sorting-algorithms-with-examples","tag-sorting-in-c","tag-sorting-in-data-structure","tag-sorting-methods","tag-sortings"],"_links":{"self":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/25266","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/comments?post=25266"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/25266\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=25266"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=25266"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=25266"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}