diff --git a/longest-substring-without-repeating-characters/krokerdile.js b/longest-substring-without-repeating-characters/krokerdile.js
new file mode 100644
index 000000000..84ce8af21
--- /dev/null
+++ b/longest-substring-without-repeating-characters/krokerdile.js
@@ -0,0 +1,23 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var lengthOfLongestSubstring = function(s) {
+    let start = 0;
+    let maxLength = 0;
+    const seen = new Map(); // 문자 -> 마지막 인덱스
+
+    for (let end = 0; end < s.length; end++) {
+        const char = s[end];
+
+        // 중복 문자가 이전에 등장했으면 start를 갱신
+        if (seen.has(char) && seen.get(char) >= start) {
+            start = seen.get(char) + 1;
+        }
+
+        seen.set(char, end); // 현재 문자 위치 갱신
+        maxLength = Math.max(maxLength, end - start + 1);
+    }
+
+    return maxLength;
+};
diff --git a/number-of-islands/krokerdile.js b/number-of-islands/krokerdile.js
new file mode 100644
index 000000000..84ce8af21
--- /dev/null
+++ b/number-of-islands/krokerdile.js
@@ -0,0 +1,23 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var lengthOfLongestSubstring = function(s) {
+    let start = 0;
+    let maxLength = 0;
+    const seen = new Map(); // 문자 -> 마지막 인덱스
+
+    for (let end = 0; end < s.length; end++) {
+        const char = s[end];
+
+        // 중복 문자가 이전에 등장했으면 start를 갱신
+        if (seen.has(char) && seen.get(char) >= start) {
+            start = seen.get(char) + 1;
+        }
+
+        seen.set(char, end); // 현재 문자 위치 갱신
+        maxLength = Math.max(maxLength, end - start + 1);
+    }
+
+    return maxLength;
+};
diff --git a/reverse-linked-list/krokerdile.js b/reverse-linked-list/krokerdile.js
new file mode 100644
index 000000000..fcedfb799
--- /dev/null
+++ b/reverse-linked-list/krokerdile.js
@@ -0,0 +1,24 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+function reverseList(head) {
+    let prev = null;
+    let curr = head;
+
+    while (curr !== null) {
+        let nextTemp = curr.next;
+        curr.next = prev;
+        prev = curr;
+        curr = nextTemp;
+    }
+
+    return prev; // prev는 새로운 head
+}
diff --git a/set-matrix-zeroes/krokerdile.js b/set-matrix-zeroes/krokerdile.js
new file mode 100644
index 000000000..73245b1e8
--- /dev/null
+++ b/set-matrix-zeroes/krokerdile.js
@@ -0,0 +1,57 @@
+/**
+ * @param {number[][]} matrix
+ * @return {void} Do not return anything, modify matrix in-place instead.
+ */
+var setZeroes = function(matrix) {
+    const m = matrix.length;
+    const n = matrix[0].length;
+    
+    let firstRowHasZero = false;
+    let firstColHasZero = false;
+
+    // 첫 행/열에 0이 있는지 확인
+    for (let i = 0; i < m; i++) {
+        if (matrix[i][0] === 0) firstColHasZero = true;
+    }
+    for (let j = 0; j < n; j++) {
+        if (matrix[0][j] === 0) firstRowHasZero = true;
+    }
+
+    // 마커로 0 표시
+    for (let i = 1; i < m; i++) {
+        for (let j = 1; j < n; j++) {
+            if (matrix[i][j] === 0) {
+                matrix[i][0] = 0; // 해당 행 마킹
+                matrix[0][j] = 0; // 해당 열 마킹
+            }
+        }
+    }
+
+    // 마커 기반으로 행/열 0 처리
+    for (let i = 1; i < m; i++) {
+        if (matrix[i][0] === 0) {
+            for (let j = 1; j < n; j++) {
+                matrix[i][j] = 0;
+            }
+        }
+    }
+    for (let j = 1; j < n; j++) {
+        if (matrix[0][j] === 0) {
+            for (let i = 1; i < m; i++) {
+                matrix[i][j] = 0;
+            }
+        }
+    }
+
+    // Step 4: 첫 행과 첫 열 처리
+    if (firstRowHasZero) {
+        for (let j = 0; j < n; j++) {
+            matrix[0][j] = 0;
+        }
+    }
+    if (firstColHasZero) {
+        for (let i = 0; i < m; i++) {
+            matrix[i][0] = 0;
+        }
+    }
+};
diff --git a/unique-paths/krokerdile.js b/unique-paths/krokerdile.js
new file mode 100644
index 000000000..3e73cd86d
--- /dev/null
+++ b/unique-paths/krokerdile.js
@@ -0,0 +1,21 @@
+/**
+ * @param {number} m
+ * @param {number} n
+ * @return {number}
+ */
+var uniquePaths = function(m, n) {
+    const memo = {};
+
+    function dfs(x, y) {
+        if (x >= m || y >= n) return 0;
+        if (x === m - 1 && y === n - 1) return 1;
+
+        const key = `${x},${y}`;
+        if (key in memo) return memo[key];
+
+        memo[key] = dfs(x + 1, y) + dfs(x, y + 1);
+        return memo[key];
+    }
+
+    return dfs(0, 0);
+};