package patterntwo.recursion;

public class substring {

// Recursive helper: counts substrings starting from index i

public static int countSubstrings(String s, int i) {

int n = s.length();

// Base case

if (i >= n) return 0;

int count = 1; // At least one char

int j = i + 1;

// Count how many same consecutive characters

while (j < n && s.charAt(j) == s.charAt(i)) {

count++;

j++;

}

// Substrings from this block = k*(k+1)/2

int blockSubstrings = (count * (count + 1)) / 2;

// Recurse from next block

return blockSubstrings + countSubstrings(s, j);

}

public static void main(String[] args) {

String s = "abcab";

int result = countSubstrings(s, 0);

System.out.println("Count: " + result); // Output: 7

}

}