LeetCode-in-Java
1759. Count Number of Homogenous Substrings
Medium
Given a string s, return the number of homogenous substrings of s. Since the answer may be too large, return it modulo 109 + 7.
A string is homogenous if all the characters of the string are the same.
A substring is a contiguous sequence of characters within a string.
Example 1:
Input: s = “abbcccaa”
Output: 13
Explanation: The homogenous substrings are listed as below:
“a” appears 3 times.
“aa” appears 1 time.
“b” appears 2 times.
“bb” appears 1 time.
“c” appears 3 times.
“cc” appears 2 times.
“ccc” appears 1 time.
3 + 1 + 2 + 1 + 3 + 2 + 1 = 13.
Example 2:
Input: s = “xy”
Output: 2
Explanation: The homogenous substrings are “x” and “y”.
Example 3:
Input: s = “zzzzz”
Output: 15
Constraints:
1 <= s.length <= 105sconsists of lowercase letters.
Solution
public class Solution {
public int countHomogenous(String s) {
int total = 0;
int count = 0;
for (int i = 0; i < s.length(); i++) {
if (i > 0 && s.charAt(i) == s.charAt(i - 1)) {
count++;
} else {
count = 1;
}
total = (total + count) % 1000000007;
}
return total;
}
}