3.longest-substring-without-repeating-characters.kt

/*
 * @lc app=leetcode id=3 lang=kotlin
 *
 * [3] Longest Substring Without Repeating Characters
 *
 * https://leetcode.com/problems/longest-substring-without-repeating-characters/description/
 *
 * algorithms
 * Medium (28.19%)
 * Total Accepted:    878.9K
 * Total Submissions: 3.1M
 * Testcase Example:  '"abcabcbb"'
 *
 * Given a string, find the length of the longest substring without repeating
 * characters.
 * 
 * 
 * Example 1:
 * 
 * 
 * Input: "abcabcbb"
 * Output: 3 
 * Explanation: The answer is "abc", with the length of 3. 
 * 
 * 
 * 
 * Example 2:
 * 
 * 
 * Input: "bbbbb"
 * Output: 1
 * Explanation: The answer is "b", with the length of 1.
 * 
 * 
 * 
 * Example 3:
 * 
 * 
 * Input: "pwwkew"
 * Output: 3
 * Explanation: The answer is "wke", with the length of 3. 
 * ⁠            Note that the answer must be a substring, "pwke" is a
 * subsequence and not a substring.
 * 
 * 
 * 
 * 
 */
class Solution {
    fun lengthOfLongestSubstring(s: String): Int {
        val mm = HashMap<Char, Int>()
        var ans = 0
        var last = -1
        for (i in s.indices) {
            last = Math.max(last, mm.getOrElse(s[i], {-1}))
            ans = Math.max(ans, i - last)
            mm[s[i]] = i
        }
        return ans
    }
}