Maps to store frequencies of elements present in left and right arrays
HashMap < Integer , Integer > freq1 = new HashMap < > ( ) ; HashMap < Integer , Integer > freq2 = new HashMap < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( freq1 . containsKey ( left [ i ] ) ) freq1 . put ( left [ i ] , freq1 . get ( left [ i ] ) + 1 ) ; else freq1 . put ( left [ i ] , 1 ) ; if ( freq2 . containsKey ( right [ i ] ) ) freq2 . put ( right [ i ] , freq2 . get ( right [ i ] ) + 1 ) ; else freq2 . put ( right [ i ] , 1 ) ; } int ans = 0 ; for ( int i = 0 ; i < n ; i ++ ) {