diff --git a/clone-graph/hoyeongkwak.ts b/clone-graph/hoyeongkwak.ts
new file mode 100644
index 000000000..acd66e7fc
--- /dev/null
+++ b/clone-graph/hoyeongkwak.ts
@@ -0,0 +1,35 @@
+/**
+ * Definition for _Node.
+ * class _Node {
+ *     val: number
+ *     neighbors: _Node[]
+ * 
+ *     constructor(val?: number, neighbors?: _Node[]) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.neighbors = (neighbors===undefined ? [] : neighbors)
+ *     }
+ * }
+ * 
+ */
+
+/*
+*/
+function cloneGraph(node: _Node | null): _Node | null {
+    const clones = new Map<_Node, _Node>()
+	const dfs = (n: _Node) => {
+        if (n === null) return n
+
+        if (clones.has(n)) {
+            return clones.get(n)
+        }
+
+        const copy = new _Node(n.val)
+        clones.set(n, copy)
+
+        for (const neighbor of n.neighbors) {
+            copy.neighbors.push(dfs(neighbor))
+        }
+        return copy
+    }
+    return dfs(node)
+};
diff --git a/longest-common-subsequence/hoyeongkwak.ts b/longest-common-subsequence/hoyeongkwak.ts
new file mode 100644
index 000000000..2caeea436
--- /dev/null
+++ b/longest-common-subsequence/hoyeongkwak.ts
@@ -0,0 +1,17 @@
+function longestCommonSubsequence(text1: string, text2: string): number {
+    const m1 = text1.length
+    const m2 = text2.length
+    
+    const dp: number[][] = Array(m1 + 1).fill(null).map(() => Array(m2 + 1).fill(0))
+
+    for (let r = 1; r <= m1; r++) {
+        for (let c = 1; c <= m2; c++) {
+            if (text1[r - 1] === text2[c - 1]) {
+                dp[r][c] = dp[r - 1][c - 1] + 1
+            } else {
+                dp[r][c] = Math.max(dp[r - 1][c], dp[r][c - 1])
+            }
+        }
+    }
+    return dp[m1][m2]
+};
diff --git a/longest-repeating-character-replacement/hoyeongkwak.ts b/longest-repeating-character-replacement/hoyeongkwak.ts
new file mode 100644
index 000000000..5d02f085b
--- /dev/null
+++ b/longest-repeating-character-replacement/hoyeongkwak.ts
@@ -0,0 +1,19 @@
+function characterReplacement(s: string, k: number): number {
+    /*
+
+    */
+    let maxLen = 0
+    let maxCnt = new Map<string, number>()
+    let start = 0
+    let maxFreq = 0
+    for (let e = 0; e < s.length; e++) {
+        maxCnt.set(s[e], (maxCnt.get(s[e]) || 0) + 1)
+        maxFreq = Math.max(maxFreq, maxCnt.get(s[e]))
+        while (e - start + 1 - maxFreq > k) {
+            maxCnt.set(s[start], maxCnt.get(s[start]) - 1)
+            start += 1
+        }
+        maxLen = Math.max(e - start + 1, maxLen)
+    }
+    return maxLen
+};
diff --git a/palindromic-substrings/hoyeongkwak.ts b/palindromic-substrings/hoyeongkwak.ts
new file mode 100644
index 000000000..5766a5616
--- /dev/null
+++ b/palindromic-substrings/hoyeongkwak.ts
@@ -0,0 +1,20 @@
+function countSubstrings(s: string): number {
+    const sLen = s.length;
+    const dp = Array(sLen).fill(null).map(() => Array(sLen).fill(false))
+    let cnt = 0
+
+    for (let i = sLen - 1; i >= 0; i--) {
+        for (let j = i; j < sLen; j++) {
+            if (i === j) {
+                dp[i][j] = true
+            } else if (j === i + 1) {
+                dp[i][j] = (s[i] === s[j])
+            } else {
+                dp[i][j] = (s[i] === s[j]) && dp[i + 1][j - 1]
+            }
+
+            if (dp[i][j]) cnt++
+        }
+    }
+    return cnt
+};
diff --git a/reverse-bits/hoyeongkwak.ts b/reverse-bits/hoyeongkwak.ts
new file mode 100644
index 000000000..085e632f4
--- /dev/null
+++ b/reverse-bits/hoyeongkwak.ts
@@ -0,0 +1,5 @@
+function reverseBits(n: number): number {
+    const binaryStr = n.toString(2).padStart(32, '0')
+    const reverseNum = binaryStr.split('').reverse().join('')
+    return parseInt(reverseNum, 2)
+};