text: Given an array arr [ ] , find the maximum j | Java implementation of the hashmap approach ; Function to find maximum index difference ; Initilaise unordered_map ; Iterate from 0 to n - 1 ; Sort arr ; Iterate from 0 to n - 1 ; Driver Code ; Function Call
code: import java . io . * ; import java . util . * ; class GFG { static int maxIndexDiff ( ArrayList < Integer > arr , int n ) { Map < Integer , ArrayList < Integer > > hashmap = new HashMap < Integer , ArrayList < Integer > > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( hashmap . containsKey ( arr . get ( i ) ) ) { hashmap . get ( arr . get ( i ) ) . add ( i ) ; } else { hashmap . put ( arr . get ( i ) , new ArrayList < Integer > ( ) ) ; hashmap . get ( arr . get ( i ) ) . add ( i ) ; } } Collections . sort ( arr ) ; int maxDiff = Integer . MIN_VALUE ; int temp = n ; for ( int i = 0 ; i < n ; i ++ ) { if ( temp > hashmap . get ( arr . get ( i ) ) . get ( 0 ) ) { temp = hashmap . get ( arr . get ( i ) ) . get ( 0 ) ; } maxDiff = Math . max ( maxDiff , hashmap . get ( arr . get ( i ) ) . get ( hashmap . get ( arr . get ( i ) ) . size ( ) - 1 ) - temp ) ; } return maxDiff ; } public static void main ( String [ ] args ) { int n = 9 ; ArrayList < Integer > arr = new ArrayList < Integer > ( Arrays . asList ( 34 , 8 , 10 , 3 , 2 , 80 , 30 , 33 , 1 ) ) ; int ans = maxIndexDiff ( arr , n ) ; System . out . println ( " The ▁ maxIndexDiff ▁ is ▁ : ▁ " + ans ) ; } }