diff --git a/longest-repeating-character-replacement/jaejeong1.kt b/longest-repeating-character-replacement/jaejeong1.kt
new file mode 100644
index 0000000000..1837947c15
--- /dev/null
+++ b/longest-repeating-character-replacement/jaejeong1.kt
@@ -0,0 +1,27 @@
+import kotlin.math.max
+
+fun characterReplacement(s: String, k: Int): Int {
+	// 시간복잡도: O(N) 공간복잡도: O(1)
+
+	val frequencyMap = mutableMapOf<Char, Int>()
+	var left = 0
+	var maxFreq = 0
+	var result = 0
+	// 처음부터 끝까지 right 순회
+	for (right in s.indices) {
+		// right 위치 문자에 빈도를 증가시키고 map 저장
+		val rightChar = s[right]
+		frequencyMap[rightChar] = frequencyMap.getOrDefault(rightChar, 0) + 1
+		maxFreq = max(maxFreq, frequencyMap[rightChar]!!)
+
+		val windowSize = right - left + 1
+		val downSizeNeeded = windowSize - maxFreq
+
+		if (downSizeNeeded > k) {
+			val leftChar = s[left]
+			frequencyMap[leftChar] = frequencyMap[leftChar]!! - 1
+			left++
+		}
+		result = max(result, right - left + 1)
+	}
+}
diff --git a/reverse-bits/jaejeong1.kt b/reverse-bits/jaejeong1.kt
new file mode 100644
index 0000000000..569e24bdee
--- /dev/null
+++ b/reverse-bits/jaejeong1.kt
@@ -0,0 +1,13 @@
+fun reverseBits(n: Int): Int {
+	var x = n
+	var result = 0
+	//시간복잡도: O(N) 공간복잡도: O(1)
+	repeat(32) {
+		// result를 왼쪽으로 1비트 밀어서 빈자리를 만듬
+		result = (result shl 1)
+		// x의 맨 오른쪽 1자리를 result의 맨 오른쪽에 할당
+		result = result or (x and 1)
+		// x 를 오른쪽으로 1비트 민다
+		x = (x ushr 1)
+	}
+}