1636 Number Of Substrings With Only 1S

Number of Substrings With Only 1s

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'.

impl Solution {
    pub fn num_sub(s: String) -> i32 {
        const MODULO: i64 = 1000000007;
        let mut total: i64 = 0;
        let mut consecutive: i64 = 0;
        for c in s.chars() {
            if c == '0' {
                total += consecutive * (consecutive + 1) / 2;
                total %= MODULO;
                consecutive = 0;
            } else {
                consecutive += 1;
            }
        }
        total += consecutive * (consecutive + 1) / 2;
        total %= MODULO;
        total as i32
    }
}