Add longest_substring_with_unique_chars

Author: marttp

rust/Sliding Windows/longest_substring_with_unique_chars.rs

@@ -0,0 +1,26 @@
+fn longest_substring_with_unique_chars(s: String) -> i32 {
+    use std::collections::HashSet;
+
+    let mut max_len = 0;
+    let mut hash_set = HashSet::new();
+    let mut left = 0;
+    let mut right = 0;
+    let s = s.as_bytes();
+
+    while right < s.len() {
+        // If we encounter a duplicate character in the window, shrink
+        // the window until it's no longer a duplicate.
+        while hash_set.contains(&s[right]) {
+            hash_set.remove(&s[left]);
+            left += 1;
+        }
+        // Once there are no more duplicates in the window, update
+        // 'max_len' if the current window is larger.
+        max_len = max_len.max(right - left + 1);
+        hash_set.insert(s[right]);
+        // Expand the window.
+        right += 1;
+    }
+
+    max_len as i32
+}