README.md

1358. Number of Substrings Containing All Three Characters

Given a string s consisting only of characters a, b and c.

Return the number of substrings containing at least one occurrence of all these characters a, b and c.

Example 1:

Input: s = "abcabc"
Output: 10
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "abc", "abca", "abcab", "abcabc", "bca", "bcab", "bcabc", "cab", "cabc" and "abc" (again).

Example 2:

Input: s = "aaacb"
Output: 3
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "aaacb", "aacb" and "acb".

Example 3:

Input: s = "abc"
Output: 1

Constraints:

• 3 <= s.length <= 5 x 10^4
• s only consists of a, b or c characters.

Solutions (Rust)

1. Solution

impl Solution {
    pub fn number_of_substrings(s: String) -> i32 {
        let s = s.as_bytes();
        let mut count = [0; 3];
        let mut i = 0;
        let mut ret = 0;

        for j in 0..s.len() {
            count[(s[j] - b'a') as usize] += 1;

            while count[0] * count[1] * count[2] > 0 {
                count[(s[i] - b'a') as usize] -= 1;
                i += 1;
            }

            ret += i;
        }

        ret as i32
    }
}