Add Kotlin leetcode 3

Author: edo-ce

kotlin/3-Longest-Substring-Without-Repeating-Characters.kt

@@ -0,0 +1,17 @@
+class Solution {
+    fun lengthOfLongestSubstring(s: String): Int {
+        val hs = HashSet<Char>()
+        var i = 0
+        var j = 0
+        var maxLength = 0
+        while (j < s.length) {
+            if (hs.contains(s[j])) {
+                hs.remove(s[i++])
+            } else {
+                hs.add(s[j++])
+                maxLength = maxLength.coerceAtLeast(hs.size)
+            }
+        }
+        return maxLength
+    }
+}