struct Solution;
impl Solution {
fn length_of_longest_substring_two_distinct(s: String) -> i32 {
let s: Vec<char> = s.chars().collect();
let mut count: Vec<usize> = vec![0; 256];
let mut start = 0;
let mut end = 0;
let mut res = 0;
let n = s.len();
let mut sum = 0;
while end < n {
if sum <= 2 {
count[s[end] as usize] += 1;
if count[s[end] as usize] == 1 {
sum += 1;
}
end += 1;
} else {
count[s[start] as usize] -= 1;
if count[s[start] as usize] == 0 {
sum -= 1;
}
start += 1;
}
if sum <= 2 {
res = res.max(end - start);
}
}
res as i32
}
}
#[test]
fn test() {
let s = "eceba".to_string();
let res = 3;
assert_eq!(Solution::length_of_longest_substring_two_distinct(s), res);
let s = "ccaabbb".to_string();
let res = 5;
assert_eq!(Solution::length_of_longest_substring_two_distinct(s), res);
}