LeetCode-in-All

3. Longest Substring Without Repeating Characters

Medium

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

Example 4:

Input: s = “”

Output: 0

Constraints:

Solution

class Solution {
    fun lengthOfLongestSubstring(s: String): Int {
        val lastIndices = IntArray(256) { -1 }
        var maxLen = 0
        var curLen = 0
        var start = 0
        for (i in s.indices) {
            val cur = s[i]
            if (lastIndices[cur.code] < start) {
                lastIndices[cur.code] = i
                curLen++
            } else {
                val lastIndex = lastIndices[cur.code]
                start = lastIndex + 1
                curLen = i - start + 1
                lastIndices[cur.code] = i
            }
            if (curLen > maxLen) {
                maxLen = curLen
            }
        }
        return maxLen
    }
}