diff --git a/combination-sum/jeongwoo903.js b/combination-sum/jeongwoo903.js
new file mode 100644
index 000000000..df651c392
--- /dev/null
+++ b/combination-sum/jeongwoo903.js
@@ -0,0 +1,29 @@
+/*
+* k: 후보 수
+* t: target / 최소 숫자
+* 시간 복잡도: O(k^t)
+* 공간 복잡도; O(k^t * t)
+*/
+
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+
+var combinationSum = function(candidates, target) {
+  const combine = (sum, path, startIndex) => {
+    if (sum > target) return [];
+    if (sum === target) return [path];
+
+    return candidates
+    .slice(startIndex)
+    .flatMap((candidate, i) =>
+      combine(sum + candidate, [...path, candidate], startIndex + i)
+    );
+  };
+
+  return candidates.flatMap((candidate, i) =>
+    combine(candidate, [candidate], i)
+  );
+};
diff --git a/decode-ways/jeongwoo903.js b/decode-ways/jeongwoo903.js
new file mode 100644
index 000000000..cd676b71c
--- /dev/null
+++ b/decode-ways/jeongwoo903.js
@@ -0,0 +1,27 @@
+/*
+* 시간 복잡도: O(n)
+* 공간 복잡도; O(n)
+*/
+
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var numDecodings = function(s) {
+  if (s.length === 0 || s[0] === "0") return 0;
+
+  let dp = new Array(s.length + 1).fill(0);
+
+  dp[0] = 1;
+  dp[1] = 1;
+
+  for (let i = 2; i <= s.length; i++) {
+    let single = s[i - 1];
+    let double = s[i - 2] + s[i - 1];
+
+    if (single >= 1 && single <= 9) dp[i] += dp[i - 1];
+    if (double >= 10 && double <= 26) dp[i] += dp[i - 2];
+  }
+
+  return dp[s.length];
+};
diff --git a/maximum-subarray/jeongwoo903.js b/maximum-subarray/jeongwoo903.js
new file mode 100644
index 000000000..002e2d030
--- /dev/null
+++ b/maximum-subarray/jeongwoo903.js
@@ -0,0 +1,21 @@
+/*
+* 시간 복잡도: O(n)
+* 공간 복잡도: O(1)
+*/
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxSubArray = function(nums) {
+  let max = nums[0];
+  let result = nums[0];
+
+  for (let index = 1; index < nums.length; index++) {
+    const num = nums[index];
+    result = Math.max(result + num, num);
+    max = Math.max(max, result);
+  }
+
+  return max;
+};
diff --git a/number-of-1-bits/jeongwoo903.js b/number-of-1-bits/jeongwoo903.js
new file mode 100644
index 000000000..c919cfe8d
--- /dev/null
+++ b/number-of-1-bits/jeongwoo903.js
@@ -0,0 +1,14 @@
+/*
+* 시간 복잡도: O(log n)
+* 공간 복잡도; O(log n)
+*/
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var hammingWeight = function(n) {
+  const dec = n.toString(2);
+  const parsedBits = [...dec].filter(item => item === '1');
+  return parsedBits.length;
+};
diff --git a/valid-palindrome/jeongwoo903.js b/valid-palindrome/jeongwoo903.js
new file mode 100644
index 000000000..3b05727f6
--- /dev/null
+++ b/valid-palindrome/jeongwoo903.js
@@ -0,0 +1,20 @@
+/*
+* 시간 복잡도: O(n)
+* 공간 복잡도; O(n)
+*
+* 과정:
+* 1. 소문자, 대문자, 숫자만 파싱
+* 2. 소문자로 변환
+* 3. 리버스 스트링과 기본 스트링과 대조
+*/
+
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function(s) {
+  const parsedString = s.replace(/[^a-zA-Z0-9]/g, '');
+  const lowerString = parsedString.toLowerCase();
+  const reverseString = lowerString.split("").reverse().join("");
+  return reverseString === lowerString;
+};