Add longest-substring-without-repeating-characters solution in TS

Author: Jeehay28

longest-substring-without-repeating-characters/Jeehay28.ts

@@ -0,0 +1,21 @@
+// TC: O(n)
+// SC: O(n)
+
+function lengthOfLongestSubstring(s: string): number {
+  let seen = new Map<string, number>();
+  let maxLength = 0;
+  let start = 0;
+
+  for (let end = 0; end < s.length; end++) {
+    const ch = s[end];
+
+    if (seen.has(ch) && seen.get(ch)! >= start) {
+      start = seen.get(ch)! + 1;
+    }
+
+    seen.set(ch, end);
+    maxLength = Math.max(maxLength, end - start + 1);
+  }
+
+  return maxLength;
+}