add: LongestSubstringWithUniqueCharsOptimized

Author: Jer3myYu

java/Sliding Windows/LongestSubstringWithUniqueCharsOptimized.java

@@ -0,0 +1,27 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class LongestSubstringWithUniqueCharsOptimized {
+    public int longestSubstringWithUniqueCharsOptimized(String s) {
+        int maxLen = 0;
+        Map<Character, Integer> prevIndexes = new HashMap<>();
+        int left, right;
+        left = 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 (prevIndexes.containsKey(s.charAt(right)) && prevIndexes.get(s.charAt(right)) >= left) {
+                // Shrink the window to exclude the previous occurrence
+                // of this character.
+                left = prevIndexes.get(s.charAt(right)) + 1;
+            }
+            // Update 'maxLen' if the current window is larger.
+            maxLen = Math.max(maxLen, right - left + 1);
+            prevIndexes.put(s.charAt(right), right);
+            // Expand the window.
+            right++;
+        }
+        return maxLen;
+    }
+}