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  1. import java.util.*;
  2.  
  3. class LogNSearch {
  4.     public static void main(String[] args) {
  5.         int[] arr = {1, 2, 2, 2, 2, 3, 4, 5, 6, 7}; // Sorted array
  6.         int target = 2; // Element to find
  7.         int index = findMiddleOccurrence(arr, target);
  8.  
  9.         System.out.println("Output: " + index);
  10.     }
  11.  
  12.     public static int findMiddleOccurrence(int[] arr, int target) {
  13.         int first = findFirstOccurrence(arr, target);
  14.         if (first == -1) {
  15.             return -1; // Target not found
  16.         }
  17.  
  18.         int last = findLastOccurrence(arr, target);
  19.  
  20.         // Calculate middle occurrence
  21.         return (first + last) / 2;
  22.     }
  23.  
  24.     private static int findFirstOccurrence(int[] arr, int target) {
  25.         int l = 0, r = arr.length - 1;
  26.         int first = -1;
  27.  
  28.         while (l <= r) {
  29.             int m = l + (r - l) / 2; // Avoid overflow
  30.             if (arr[m] >= target) {
  31.                 if (arr[m] == target) {
  32.                     first = m; // Update first occurrence
  33.                 }
  34.                 r = m - 1; // Search left
  35.             } else {
  36.                 l = m + 1; // Search right
  37.             }
  38.         }
  39.         return first;
  40.     }
  41.  
  42.     private static int findLastOccurrence(int[] arr, int target) {
  43.         int l = 0, r = arr.length - 1;
  44.         int last = -1;
  45.  
  46.         while (l <= r) {
  47.             int m = l + (r - l) / 2; // Avoid overflow
  48.             if (arr[m] <= target) {
  49.                 if (arr[m] == target) {
  50.                     last = m; // Update last occurrence
  51.                 }
  52.                 l = m + 1; // Search right
  53.             } else {
  54.                 r = m - 1; // Search left
  55.             }
  56.         }
  57.         return last;
  58.     }
  59. }
  60.  
Success #stdin #stdout 0.11s 55320KB
comments (?)
stdin 
Standard input is empty
stdout 
Output: 2
https://ideone.com/15tOn8
language:
Java (HotSpot 12)
created:
1 hour ago
visibility:
public

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