Check if two arrays are permutations of each other - GeeksQuiz

Check if two arrays are permutations of each other - GeeksQuiz
Given two unsorted arrays of same size, write a function that returns true if two arrays are permutations of each other, otherwise false.

A Simple Solution is sort both arrays and compare sorted arrays. Time complexity of this solution is O(nLogn)

A Better Solution is to use Hashing.
1) Create a Hash Map for all the elements of arr1[] such that array elements are keys and their counts are values.
2) Traverse arr2[] and search for each element of arr2[] in the Hash Map. If element is found then decrement its count in hash map. If not found, then return false.
3) If all elements are found then return true.

// A Java program to find one array is permutation of other array import java.util.HashMap;   class Permutaions {     // Returns true if arr1[] and arr2[] are permutations of each other     static Boolean arePermutations(int arr1[], int arr2[])     {         // Creates an empty hashMap hM         HashMap<Integer, Integer> hM = new HashMap<Integer, Integer>();           // Traverse through the first array and add elements to hash map         for (int i = 0; i < arr1.length; i++)         {             int x = arr1[i];             if (hM.get(x) == null)                 hM.put(x, 1);             else             {                 int k = hM.get(x);                 hM.put(x, k+1);             }         }           // Traverse through second array and check if every element is         // present in hash map         for (int i = 0; i < arr2.length; i++)         {             int x = arr2[i];               // If element is not present in hash map or element             // is not present less number of times             if (hM.get(x) == null || hM.get(x) == 0)                 return false;               int k = hM.get(x);             hM.put(x, k-1);         }         return true;     }

http://www.algoqueue.com/algoqueue/default/view/3735552/check-if-two-arrays-are-permutation-of-each-other

public boolean checkPermutation(int[] array1, int[] array2){

     /* If two arrays have different length - not a permutation*/
     if (array1.length !== array2.length)
        return false;

     /* Sort 1st array */
     Arrays.sort(array1);

     /* Sort 2nd array */
     Arrays.sort(array2);

     for(int i = 0; i  <  array1.length; i++){
           if(array1[i] !== array2[i])
              return false;       
     }
     
     return true;
 }

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