CountHomogeneousSubstrings.java

/*https://leetcode.com/problems/count-number-of-homogenous-substrings/*/

class Solution {
    public int countHomogenous(String s) {
        long consecutiveCount = 0, result = 0, mod = 1000000007;
        for (int i = 0; i < s.length(); ++i)
        {
            if (i == 0)
                ++consecutiveCount;
            else if (s.charAt(i-1) == s.charAt(i))
                ++consecutiveCount;
            else
            {
                result += ((consecutiveCount*(consecutiveCount+1))/2)%mod;
                result %= mod;
                consecutiveCount = 1;
            }
        }
        result += ((consecutiveCount*(consecutiveCount+1))/2)%mod;
        result %= mod;
        return (int)(result%mod);
    }
}

class Solution {
    public int countHomogenous(String s) {
        char prev='\0';
        long res=0;
        int c=0;
        for(char i:s.toCharArray())
        {
            if(i!=prev)
            {
                c=1;
                prev=i;
            }
            else c++;
            res+=c;
        }
        return (int)(res%(int)(1e9+7));
    }
}