Change the array into a permutation of numbers from 1 to n | Java program to make a permutation of numbers from 1 to n using minimum changes . ; Store counts of all elements . ; Find next missing element to put in place of current element . ; Replace with next missing and insert the missing element in hash . ; Driver Code
import java . util . * ; class GFG { static void makePermutation ( int [ ] a , int n ) { HashMap < Integer , Integer > count = new HashMap < Integer , Integer > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( count . containsKey ( a [ i ] ) ) { count . put ( a [ i ] , count . get ( a [ i ] ) + 1 ) ; } else { count . put ( a [ i ] , 1 ) ; } } int next_missing = 1 ; for ( int i = 0 ; i < n ; i ++ ) { if ( count . containsKey ( a [ i ] ) && count . get ( a [ i ] ) != 1 a [ i ] > n a [ i ] < 1 ) { count . put ( a [ i ] , count . get ( a [ i ] ) - 1 ) ; while ( count . containsKey ( next_missing ) ) next_missing ++ ; a [ i ] = next_missing ; count . put ( next_missing , 1 ) ; } } } public static void main ( String [ ] args ) { int A [ ] = { 2 , 2 , 3 , 3 } ; int n = A . length ; makePermutation ( A , n ) ; for ( int i = 0 ; i < n ; i ++ ) System . out . print ( A [ i ] + " ▁ " ) ; } }