Given a binary string s (a string consisting only of '0' and '1's).
Return the number of substrings with all characters 1's.
Since the answer may be too large, return it modulo 10^9 + 7.
Example 1:
Input: s = "0110111"
Output: 9
Explanation: There are 9 substring in total with only 1's characters.
"1" -> 5 times.
"11" -> 3 times.
"111" -> 1 time.
Example 2:
Input: s = "101"
Output: 2
Explanation: Substring "1" is shown 2 times in s.
Example 3:
Input: s = "111111"
Output: 21
Explanation: Each substring contains only 1's characters.
Example 4:
Input: s = "000"
Output: 0
Constraints:
s[i] == '0' or s[i] == '1'
1 <= s.length <= 10^5
class Solution {
public int numSub(String s) {
int count=0;
int res=0;
for(int i=0;i<s.length();i++){
count=s.charAt(i)=='1'?count+1:0;
res=(res+count)%(int)(1e9+7);
}
return res;
}
}