From d39ddcdd73d9504c1f622fb0a9d994b6b66f097c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=B5=9C=ED=98=84=EC=A0=95?= <hjchoi.dev@gmail.com>
Date: Sun, 3 Aug 2025 22:42:53 +0900
Subject: [PATCH 1/5] Add valid palindrome solution

---
 valid-palindrome/hyunjung-choi.kt | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 valid-palindrome/hyunjung-choi.kt

diff --git a/valid-palindrome/hyunjung-choi.kt b/valid-palindrome/hyunjung-choi.kt
new file mode 100644
index 000000000..d96360468
--- /dev/null
+++ b/valid-palindrome/hyunjung-choi.kt
@@ -0,0 +1,9 @@
+import java.util.Locale.getDefault
+
+class Solution {
+    fun isPalindrome(s: String): Boolean {
+        if (s.isBlank()) return true
+        val cleanedString = s.trim().filter { it.isLetterOrDigit() }.lowercase(getDefault())
+        return cleanedString == cleanedString.reversed()
+    }
+}

From ee4469d80abce17c3f79f6432f2f0df9296ffbd8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=B5=9C=ED=98=84=EC=A0=95?= <hjchoi.dev@gmail.com>
Date: Mon, 4 Aug 2025 11:10:35 +0900
Subject: [PATCH 2/5] Add number of 1 bits solution

---
 number-of-1-bits/hyunjung-choi.kt | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 number-of-1-bits/hyunjung-choi.kt

diff --git a/number-of-1-bits/hyunjung-choi.kt b/number-of-1-bits/hyunjung-choi.kt
new file mode 100644
index 000000000..d16916f1c
--- /dev/null
+++ b/number-of-1-bits/hyunjung-choi.kt
@@ -0,0 +1,3 @@
+class Solution {
+    fun hammingWeight(n: Int) = Integer.bitCount(n)
+}

From 0f731bc38e0e7bcd2a00437d5f0072d37ba22c70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=B5=9C=ED=98=84=EC=A0=95?= <hjchoi.dev@gmail.com>
Date: Tue, 5 Aug 2025 20:08:42 +0900
Subject: [PATCH 3/5] Add combination sum solution

---
 combination-sum/hyunjung-choi.kt | 43 ++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 combination-sum/hyunjung-choi.kt

diff --git a/combination-sum/hyunjung-choi.kt b/combination-sum/hyunjung-choi.kt
new file mode 100644
index 000000000..615dc915b
--- /dev/null
+++ b/combination-sum/hyunjung-choi.kt
@@ -0,0 +1,43 @@
+class Solution {
+    fun combinationSum(candidates: IntArray, target: Int): List<List<Int>> {
+        val result = mutableListOf<List<Int>>()
+        val currentCombination = mutableListOf<Int>()
+
+        candidates.sort()
+
+        backtrack(candidates, target, 0, currentCombination, result)
+
+        return result
+    }
+
+    private fun backtrack(
+        candidates: IntArray,
+        remainingTarget: Int,
+        startIndex: Int,
+        currentCombination: MutableList<Int>,
+        result: MutableList<List<Int>>
+    ) {
+        if (remainingTarget == 0) {
+            result.add(currentCombination.toList())
+            return
+        }
+
+        if (remainingTarget < 0) {
+            return
+        }
+
+        for (i in startIndex until candidates.size) {
+            val candidate = candidates[i]
+
+            if (candidate > remainingTarget) {
+                break
+            }
+
+            currentCombination.add(candidate)
+
+            backtrack(candidates, remainingTarget - candidate, i, currentCombination, result)
+
+            currentCombination.removeAt(currentCombination.size - 1)
+        }
+    }
+}

From 40601bec2bd998abc83e028f15e0e1419c1ed3fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=B5=9C=ED=98=84=EC=A0=95?= <hjchoi.dev@gmail.com>
Date: Wed, 6 Aug 2025 23:00:30 +0900
Subject: [PATCH 4/5] Add decode ways solution

---
 decode-ways/hyunjung-choi.kt | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 decode-ways/hyunjung-choi.kt

diff --git a/decode-ways/hyunjung-choi.kt b/decode-ways/hyunjung-choi.kt
new file mode 100644
index 000000000..f77be775b
--- /dev/null
+++ b/decode-ways/hyunjung-choi.kt
@@ -0,0 +1,27 @@
+class Solution {
+    fun numDecodings(s: String): Int {
+        if (s.isEmpty() || s[0] == '0') return 0
+
+        val n = s.length
+        val dp = IntArray(n + 1)
+
+        dp[0] = 1
+        dp[1] = 1
+
+        for (i in 2..n) {
+            val currentChar = s[i - 1]
+            val prevChar = s[i - 2]
+
+            if (currentChar != '0') {
+                dp[i] += dp[i - 1]
+            }
+
+            val twoDigit = (prevChar - '0') * 10 + (currentChar - '0')
+            if (twoDigit in 10..26) {
+                dp[i] += dp[i - 2]
+            }
+        }
+
+        return dp[n]
+    }
+}

From abd7113f1d16c805d267068c6a6fba6ff3f20d0d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EC=B5=9C=ED=98=84=EC=A0=95?= <hjchoi.dev@gmail.com>
Date: Thu, 7 Aug 2025 16:02:38 +0900
Subject: [PATCH 5/5] Add maximum subarray solution

---
 maximum-subarray/hyunjung-choi.kt | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 maximum-subarray/hyunjung-choi.kt

diff --git a/maximum-subarray/hyunjung-choi.kt b/maximum-subarray/hyunjung-choi.kt
new file mode 100644
index 000000000..d859d1014
--- /dev/null
+++ b/maximum-subarray/hyunjung-choi.kt
@@ -0,0 +1,13 @@
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        var currentSum = nums[0]
+        var maxSum = nums[0]
+
+        for (i in 1 until nums.size) {
+            currentSum = if (currentSum < 0) nums[i] else currentSum + nums[i]
+            maxSum = maxOf(currentSum, maxSum)
+        }
+
+        return maxSum
+    }
+}