Sub | C ++ implementation of above approach ; Function that counts all the sub - strings of length ' k ' which have all identical characters ; count of sub - strings , length , initial position of sliding window ; map to store the frequency of the characters of sub - string ; increase the frequency of the character and length of the sub - string ; if the length of the sub - string is greater than K ; remove the character from the beginning of sub - string ; if the length of the sub string is equal to k and frequency of one of its characters is equal to the length of the sub - string i . e . all the characters are same increase the count ; display the number of valid sub - strings ; Driver code
#include <bits/stdc++.h> NEW_LINE using namespace std ; void solve ( string s , int k ) { int count = 0 , length = 0 , pos = 0 ; map < char , int > m ; for ( int i = 0 ; i < s . length ( ) ; i ++ ) { m [ s [ i ] ] ++ ; length ++ ; if ( length > k ) { m [ s [ pos ++ ] ] -- ; length -- ; } if ( length == k && m [ s [ i ] ] == length ) count ++ ; } cout << count << endl ; } int main ( ) { string s = " aaaabbbccdddd " ; int k = 4 ; solve ( s , k ) ; return 0 ; }