leetcode 1180. Count Substrings with Only One Distinct Letter
Given a string S, return the number of substrings that have only one distinct letter.Example 1:
Input: S = "aaaba"
Output: 8
Explanation: The substrings with one distinct letter are "aaa", "aa", "a", "b".
"aaa" occurs 1 time.
"aa" occurs 2 times.
"a" occurs 4 times.
"b" occurs 1 time.
So the answer is 1 + 2 + 4 + 1 = 8.
Example 2:
Input: S = "aaaaaaaaaa"
Output: 55
Constraints:
1 <= S.length <= 1000
S consists of only lowercase English letters.
class Solution {
public int countLetters(String S) {
if (S.length() == 0) return 0;
if (S.length() == 1) return 1;
int sum = 0;
String remain = "";
Set <String> set = new HashSet<>();
String init = S.substring(0,1);
set.add(init);
for(int i = 0; i< S.length(); i++){
if(S.substring(i,i+1).equals(init)) {
remain = remain + S.substring(i,i+1);
set.add(remain + S.substring(i,i+1));
}
else {
remain = "";
init = S.substring(i,i+1);
set.add(init);
}
}
Iterator<String> iterator = set.iterator();
while(iterator.hasNext()) {
sum = sum + compare(S,iterator.next());
}
return sum;
}
public int compare(String S, String s){
int sum = 0;
for(int i = 0; i<= S.length() - s.length(); i++){
if(S.substring(i,i+s.length()).equals(s)) sum ++;
}
return sum;
}
}
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