Count common characters in two strings | Java implementation of the approach ; Function to return the count of valid indices pairs ; To store the frequencies of characters of string s1 and s2 ; To store the count of valid pairs ; Update the frequencies of the characters of string s1 ; Update the frequencies of the characters of string s2 ; Find the count of valid pairs ; Driver code
import java . util . * ; class GFG { static int countPairs ( String s1 , int n1 , String s2 , int n2 ) { int [ ] freq1 = new int [ 26 ] ; int [ ] freq2 = new int [ 26 ] ; Arrays . fill ( freq1 , 0 ) ; Arrays . fill ( freq2 , 0 ) ; int i , count = 0 ; for ( i = 0 ; i < n1 ; i ++ ) freq1 [ s1 . charAt ( i ) - ' a ' ] ++ ; for ( i = 0 ; i < n2 ; i ++ ) freq2 [ s2 . charAt ( i ) - ' a ' ] ++ ; for ( i = 0 ; i < 26 ; i ++ ) count += ( Math . min ( freq1 [ i ] , freq2 [ i ] ) ) ; return count ; } public static void main ( String args [ ] ) { String s1 = " geeksforgeeks " , s2 = " platformforgeeks " ; int n1 = s1 . length ( ) , n2 = s2 . length ( ) ; System . out . println ( countPairs ( s1 , n1 , s2 , n2 ) ) ; } }