description

Given a string s, find the length of the longest substring without duplicate characters.

 

Example 1:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

 

Constraints:

  • 0 <= s.length <= 5 * 104
  • s consists of English letters, digits, symbols and spaces.

submission

impl Solution {
    pub fn length_of_longest_substring(s: String) -> i32 {
        let mut ans = 0;
        // this marks the left side of sliding window
        let mut first = 0;
        // cache the last occurrence of different char
        // we use array to optimize hashmap cost
        let mut indices = [0; 256];
        for (idx, ch) in s.chars().enumerate() {
            // update left of sliding window
            first = first.max(indices[ch as usize]);
            // update answer
            ans = ans.max(idx as i32 - first + 1);
            // cache indices
            indices[ch as usize] = idx as i32 + 1;
        }
        ans
    }
}