diff --git a/longest-substring-without-repeating-characters/hwanmini.js b/longest-substring-without-repeating-characters/hwanmini.js
new file mode 100644
index 000000000..890797fab
--- /dev/null
+++ b/longest-substring-without-repeating-characters/hwanmini.js
@@ -0,0 +1,28 @@
+// 시간복잡도: O(n)
+// 공간복잡도: O(n)
+
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var lengthOfLongestSubstring = function(s) {
+    let maxCount = 0;
+    const map = new Map()
+
+    let leftIdx = 0;
+    for (let rightIdx = 0 ; rightIdx < s.length; rightIdx++) {
+        const char = s[rightIdx]
+        if (map.has(char) && map.get(char) >= leftIdx) leftIdx = map.get(char) + 1;
+        map.set(char, rightIdx)
+        maxCount = Math.max(maxCount, rightIdx - leftIdx + 1)
+    }
+
+    return maxCount
+};
+
+
+console.log(lengthOfLongestSubstring("abcabcbb"))
+console.log(lengthOfLongestSubstring("bbbbb"))
+console.log(lengthOfLongestSubstring("pwwkew"))
+console.log(lengthOfLongestSubstring("abba"))
+