Add Longest Substring With Unique Chars Optimized

Author: marttp

kotlin/Sliding Windows/LongestSubstringWithUniqueCharsOptimized.kt

@@ -0,0 +1,22 @@
+fun longestSubstringWithUniqueCharsOptimized(s: String): Int {
+    var maxLen = 0
+    val prevIndexes = mutableMapOf<Char, Int>()
+    var left = 0
+    var right = 0
+    while (right < s.length) {
+        // If a previous index of the current character is present
+        // in the current window, it's a duplicate character in the
+        // window.
+        if (s[right] in prevIndexes && prevIndexes[s[right]]!! >= left) {
+            // Shrink the window to exclude the previous occurrence
+            // of this character.
+            left = prevIndexes[s[right]]!! + 1
+        }
+        // Update 'maxLen' if the current window is larger.
+        maxLen = maxOf(maxLen, right - left + 1)
+        prevIndexes[s[right]] = right
+        // Expand the window.
+        right++
+    }
+    return maxLen
+}