add: LongestSubstringWithUniqueChars

Author: Jer3myYu

java/Sliding Windows/LongestSubstringWithUniqueChars.java

@@ -0,0 +1,26 @@
+import java.util.HashSet;
+import java.util.Set;
+
+public class LongestSubstringWithUniqueChars {
+    public int longestSubstringWithUniqueChars(String s) {
+        int maxLen = 0;
+        Set<Character> hashSet = new HashSet<>();
+        int left, right;
+        left = right = 0;
+        while (right < s.length()) {
+            // If we encounter a duplicate character in the window, shrink 
+            // the window until it's no longer a duplicate.
+            while (hashSet.contains(s.charAt(right))) {
+                hashSet.remove(s.charAt(left));
+                left++;
+            }
+            // Once there are no more duplicates in the window, update
+            // 'max_len' if the current window is larger.
+            maxLen = Math.max(maxLen, right - left + 1);
+            hashSet.add(s.charAt(right));
+            // Expand the window.
+            right++;
+        }
+        return maxLen;
+    }
+}