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1636. Number Of Substrings With Only 1s

Math String

Problem - Number Of Substrings With Only 1s

Medium

Given a binary string s, return the number of substrings with all characters 1's. Since the answer may be too large, return it modulo 109 + 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.

 

Constraints:

  • 1 <= s.length <= 105
  • s[i] is either '0' or '1'.

Solutions

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class Solution:
    def numSub(self, s: str) -> int:
        result = count = 0
        for char in s:
            if char == "1":
                count += 1
            else:
                count = 0
            result += count
        return result % (10**9 + 7)

Submission Stats:

  • Runtime: 19 ms (45.69%)
  • Memory: 18.3 MB (40.82%)