From 3475a97294546681d5432391d84327a0dad4f6a0 Mon Sep 17 00:00:00 2001
From: Eunice Hong <dev@eunice-hong.com>
Date: Wed, 16 Apr 2025 15:48:37 +0900
Subject: [PATCH 1/3] solve: Week 03 valid palindrome

---
 valid-palindrome/eunice-hong.ts | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 valid-palindrome/eunice-hong.ts

diff --git a/valid-palindrome/eunice-hong.ts b/valid-palindrome/eunice-hong.ts
new file mode 100644
index 000000000..736a84505
--- /dev/null
+++ b/valid-palindrome/eunice-hong.ts
@@ -0,0 +1,30 @@
+function isPalindrome(s: string): boolean {
+  // 1. filter out non-alphanumeric characters
+  const validChars =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnlopqrstuvwxyz0123456789";
+
+  // 2. compare the first and last characters
+  let i = 0;
+  let j = s.length - 1;
+
+  while (i < j) {
+    const head = s[i];
+    const tail = s[j];
+
+    if (!validChars.includes(head)) {
+      // 3. if the characters are not alphanumeric, move the pointer inward
+      i++;
+    } else if (!validChars.includes(tail)) {
+      // 3. if the characters are not alphanumeric, move the pointer inward
+      j--;
+    } else if (head.toLowerCase() !== tail.toLowerCase()) {
+      // 4. if the characters are not the same, return false
+      return false;
+    } else {
+      // 5. if the characters are the same, move the pointers inward
+      i++;
+      j--;
+    }
+  }
+  return true;
+}

From b2ce37e897bfb8d07e2276b93e9e62e682b57196 Mon Sep 17 00:00:00 2001
From: Eunice Hong <dev@eunice-hong.com>
Date: Wed, 16 Apr 2025 15:59:22 +0900
Subject: [PATCH 2/3] solve: Week 03 number of 1 bits

---
 number-of-1-bits/eunice-hong.ts | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 number-of-1-bits/eunice-hong.ts

diff --git a/number-of-1-bits/eunice-hong.ts b/number-of-1-bits/eunice-hong.ts
new file mode 100644
index 000000000..c3127d39c
--- /dev/null
+++ b/number-of-1-bits/eunice-hong.ts
@@ -0,0 +1,7 @@
+function hammingWeight(n: number): number {
+  // 1. convert the number to a binary string
+  const binaryString = n.toString(2);
+
+  // 2. count the number of 1s in the binary string
+  return binaryString.split("").filter((char) => char === "1").length;
+}

From 5e375a04ef1ddc5abc45648790016d3eee5cd374 Mon Sep 17 00:00:00 2001
From: eunice-hong <dev@eunice-hong.com>
Date: Fri, 18 Apr 2025 11:52:12 +0900
Subject: [PATCH 3/3] solve: Week 03 combination sum

---
 combination-sum/eunice-hong.ts | 41 ++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 combination-sum/eunice-hong.ts

diff --git a/combination-sum/eunice-hong.ts b/combination-sum/eunice-hong.ts
new file mode 100644
index 000000000..c6fd2fe21
--- /dev/null
+++ b/combination-sum/eunice-hong.ts
@@ -0,0 +1,41 @@
+/**
+ * Finds all unique combinations of numbers from the candidates array that sum up to the target.
+ * 
+ * @param candidates - An array of numbers.
+ * @param target - The target sum.
+ * @returns An array of arrays, each containing a unique combination of numbers that sum up to the target.
+ * 
+ * Time Complexity: O(n^2)
+ * Space Complexity: O(n)
+ */
+function combinationSum(candidates: number[], target: number): number[][] {
+    // 1. Initialize result array
+    let combinations: number[][] = [];
+    let candidate: number[] = [];
+
+    // 2. Define recursive function
+    function combination(start: number, total: number) {
+        console.log(`start:${start}, total:${total}`)
+        if (target < total) {
+          // 3. If total is greater than target, return
+            return;
+        } else if (target === total) {
+            // 4. If total is equal to target, push candidate to result
+            combinations.push([...candidate])
+            return;
+        } else {
+          // 5. If total is less than target, iterate through candidates
+            for (let i = start; i < candidates.length; i++) {
+                // 6. Push candidate to result
+                candidate.push(candidates[i])
+                // 7. Recursively call combination function
+                combination(i, total + candidates[i])
+                // 8. Pop candidate from result
+                candidate.pop();
+            }
+        }
+    }
+    combination(0, 0);
+
+    return combinations;
+};