Case | Java implementation of the approach ; To store the frequencies of the lowercase and the uppercase characters in the given string ; If current character is lowercase then increment its frequency in the lower [ ] array ; Else increment in the upper [ ] array ; Pointers that point to the smallest lowercase and the smallest uppercase characters respectively in the given string ; For every character in the given string ; If the current character is lowercase then replace it with the smallest lowercase character available ; Decrement the frequency of the used character ; Else replace it with the smallest uppercase character available ; Decrement the frequency of the used character ; Return the sorted string ; Driver code
import java . lang . Character ; class GFG { static int MAX = 26 ; public static String getSortedString ( StringBuilder s , int n ) { int [ ] lower = new int [ MAX ] ; int [ ] upper = new int [ MAX ] ; for ( int i = 0 ; i < n ; i ++ ) { if ( Character . isLowerCase ( s . charAt ( i ) ) ) lower [ s . charAt ( i ) - ' a ' ] ++ ; else if ( Character . isUpperCase ( s . charAt ( i ) ) ) upper [ s . charAt ( i ) - ' A ' ] ++ ; } int i = 0 , j = 0 ; while ( i < MAX && lower [ i ] == 0 ) i ++ ; while ( j < MAX && upper [ j ] == 0 ) j ++ ; for ( int k = 0 ; k < n ; k ++ ) { if ( Character . isLowerCase ( s . charAt ( k ) ) ) { while ( lower [ i ] == 0 ) i ++ ; s . setCharAt ( k , ( char ) ( i + ' a ' ) ) ; lower [ i ] -- ; } else if ( Character . isUpperCase ( s . charAt ( k ) ) ) { while ( upper [ j ] == 0 ) j ++ ; s . setCharAt ( k , ( char ) ( j + ' A ' ) ) ; upper [ j ] -- ; } } return s . toString ( ) ; } public static void main ( String [ ] args ) { StringBuilder s = new StringBuilder ( " gEeksfOrgEEkS " ) ; int n = s . length ( ) ; System . out . println ( getSortedString ( s , n ) ) ; } }