From f70016b4cd8979dd886a4684914619202003f570 Mon Sep 17 00:00:00 2001
From: sadie100 <03sadie@gmail.com>
Date: Mon, 16 Mar 2026 20:43:21 +0900
Subject: [PATCH 1/3] sadie100: valid palindrome solution

---
 valid-palindrome/sadie100.ts | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 valid-palindrome/sadie100.ts

diff --git a/valid-palindrome/sadie100.ts b/valid-palindrome/sadie100.ts
new file mode 100644
index 000000000..0258a1116
--- /dev/null
+++ b/valid-palindrome/sadie100.ts
@@ -0,0 +1,23 @@
+/*
+s에서 알파벳과 숫자가 아닌 글자를 다 날리고, 스택에 문자를 절반까지 담은 후 절반 이후부터는 꺼내가며 앞뒤 레터가 일치하는지 확인한다
+
+시간복잡도 : O(N) (N은 s의 길이)
+공간복잡도 : O(N) (스택)
+*/
+
+function isPalindrome(s: string): boolean {
+  const newStr = s.replace(/[^a-zA-Z0-9]/g, '').toLowerCase()
+  const isStrEven = newStr.length % 2 === 0
+  const lenHalf = Math.floor(newStr.length / 2)
+  const stack = []
+  for (let i = 0; i < newStr.length; i++) {
+    if (i < lenHalf) {
+      stack.push(newStr[i])
+    } else {
+      if (!isStrEven && i === lenHalf) continue
+      const isSame = newStr[i] === stack.pop()
+      if (!isSame) return false
+    }
+  }
+  return true
+}

From 0439ac7eaa2ddbb62990f8e7836f2322afa8b91b Mon Sep 17 00:00:00 2001
From: sadie100 <03sadie@gmail.com>
Date: Tue, 17 Mar 2026 20:25:24 +0900
Subject: [PATCH 2/3] sadie100: number of 1 bits solution

---
 number-of-1-bits/sadie100.ts | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 number-of-1-bits/sadie100.ts

diff --git a/number-of-1-bits/sadie100.ts b/number-of-1-bits/sadie100.ts
new file mode 100644
index 000000000..deb1a4af6
--- /dev/null
+++ b/number-of-1-bits/sadie100.ts
@@ -0,0 +1,14 @@
+/**
+n을 이진수 변환하고 1의 개수를 센다
+
+시간복잡도 O(N) (N은 숫자 n의 비트 개수)
+ */
+
+function hammingWeight(n: number): number {
+  const binaryNum = n.toString(2)
+  let result = 0
+  for (let char of binaryNum) {
+    if (char === '1') result += 1
+  }
+  return result
+}

From af27ccbea93050fbcce75f65f7c17f9e3069520d Mon Sep 17 00:00:00 2001
From: sadie100 <03sadie@gmail.com>
Date: Wed, 18 Mar 2026 18:47:29 +0900
Subject: [PATCH 3/3] sadie100: combination sum solution

---
 combination-sum/sadie100.ts | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 combination-sum/sadie100.ts

diff --git a/combination-sum/sadie100.ts b/combination-sum/sadie100.ts
new file mode 100644
index 000000000..97f4afc9e
--- /dev/null
+++ b/combination-sum/sadie100.ts
@@ -0,0 +1,28 @@
+/*
+dfs로 각 candidates를 돌면서 target과 같아지는 순간에 result를 반환한다.
+
+같은 조합이 중복됨을 피하기 위해 candidates를 정렬하고, 각 숫자보다 크거나 같은 candidate만 탐색한다.
+
+시간복잡도 : O(N^(T/min(c))) - N은 candidates의 수, T는 타겟, c는 candidates.
+타겟을 candidates의 최소값으로 나눈 값이 최대 깊이이므로 최악의 경우 해당 횟수만큼 반복해서 배열을 탐색함
+*/
+
+function combinationSum(candidates: number[], target: number): number[][] {
+  candidates.sort((a, b) => a - b)
+  const result = []
+  const search = (idx, nums, sum) => {
+    if (sum === target) {
+      result.push(nums)
+      return
+    }
+    for (let i = idx; i < candidates.length; i++) {
+      const num = candidates[i]
+      if (sum + num > target) return
+      search(i, [...nums, num], sum + num)
+    }
+  }
+
+  search(0, [], 0)
+
+  return result
+}