diff --git a/linked-list-cycle/hsskey.js b/linked-list-cycle/hsskey.js
new file mode 100644
index 000000000..0dacc476b
--- /dev/null
+++ b/linked-list-cycle/hsskey.js
@@ -0,0 +1,27 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+
+/**
+ * @param {ListNode} head
+ * @return {boolean}
+ */
+var hasCycle = function(head) {
+    let slow = head;
+    let fast = head;
+
+    while (fast !== null && fast.next !== null) {
+        slow = slow.next;
+        fast = fast.next.next;
+
+        if (slow === fast) {
+            return true;
+        }
+    }
+
+    return false;
+};
diff --git a/maximum-product-subarray/hsskey.js b/maximum-product-subarray/hsskey.js
new file mode 100644
index 000000000..fe07f1fe7
--- /dev/null
+++ b/maximum-product-subarray/hsskey.js
@@ -0,0 +1,25 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxProduct = function(nums) {
+    let res = Math.max(...nums);
+    let curMin = 1;
+    let curMax = 1;
+
+    for (let n of nums) {
+        if (n === 0) {
+            curMin = 1;
+            curMax = 1;
+            continue;
+        }
+
+        let tmp = curMax * n;
+        curMax = Math.max(n * curMax, n * curMin, n);
+        curMin = Math.min(tmp, n * curMin, n);
+
+        res = Math.max(res, curMax);
+    }
+
+    return res;
+};
diff --git a/minimum-window-substring/hsskey.js b/minimum-window-substring/hsskey.js
new file mode 100644
index 000000000..1c0e60169
--- /dev/null
+++ b/minimum-window-substring/hsskey.js
@@ -0,0 +1,55 @@
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {string}
+ */
+var minWindow = function(s, t) {
+    if (s.length === 0 || t.length === 0) return "";
+    
+    const dictT = {};
+    for (let char of t) {
+        dictT[char] = (dictT[char] || 0) + 1;
+    }
+    
+    const required = Object.keys(dictT).length;
+    let formed = 0;
+    
+    const windowCounts = {};
+    
+    let left = 0, right = 0;
+    
+    let minLen = Infinity;
+    let minLeft = 0, minRight = 0;
+    
+    while (right < s.length) {
+        const character = s[right];
+        windowCounts[character] = (windowCounts[character] || 0) + 1;
+        
+        if (dictT[character] && windowCounts[character] === dictT[character]) {
+            formed++;
+        }
+        
+        while (left <= right && formed === required) {
+            const currentLen = right - left + 1;
+            
+            if (currentLen < minLen) {
+                minLen = currentLen;
+                minLeft = left;
+                minRight = right;
+            }
+            
+            const leftChar = s[left];
+            windowCounts[leftChar]--;
+            
+            if (dictT[leftChar] && windowCounts[leftChar] < dictT[leftChar]) {
+                formed--;
+            }
+            
+            left++;
+        }
+        
+        right++;
+    }
+    
+    return minLen === Infinity ? "" : s.substring(minLeft, minRight + 1);
+};
diff --git a/pacific-atlantic-water-flow/hsskey.js b/pacific-atlantic-water-flow/hsskey.js
new file mode 100644
index 000000000..ad0eef8ab
--- /dev/null
+++ b/pacific-atlantic-water-flow/hsskey.js
@@ -0,0 +1,51 @@
+/**
+ * @param {number[][]} heights
+ * @return {number[][]}
+ */
+var pacificAtlantic = function(heights) {
+    const ROWS = heights.length;
+    const COLS = heights[0].length;
+
+    const pac = new Set();
+    const atl = new Set();
+
+    const dfs = (r, c, visit, prevHeight) => {
+        const key = `${r},${c}`;
+        if (
+            visit.has(key) ||
+            r < 0 || c < 0 || r >= ROWS || c >= COLS ||
+            heights[r][c] < prevHeight
+        ) {
+            return;
+        }
+
+        visit.add(key);
+
+        dfs(r + 1, c, visit, heights[r][c]);
+        dfs(r - 1, c, visit, heights[r][c]);
+        dfs(r, c + 1, visit, heights[r][c]);
+        dfs(r, c - 1, visit, heights[r][c]);
+    };
+
+    for (let c = 0; c < COLS; c++) {
+        dfs(0, c, pac, heights[0][c]);               // Top row (Pacific)
+        dfs(ROWS - 1, c, atl, heights[ROWS - 1][c]);  // Bottom row (Atlantic)
+    }
+
+    for (let r = 0; r < ROWS; r++) {
+        dfs(r, 0, pac, heights[r][0]);               // Left col (Pacific)
+        dfs(r, COLS - 1, atl, heights[r][COLS - 1]); // Right col (Atlantic)
+    }
+
+    const res = [];
+    for (let r = 0; r < ROWS; r++) {
+        for (let c = 0; c < COLS; c++) {
+            const key = `${r},${c}`;
+            if (pac.has(key) && atl.has(key)) {
+                res.push([r, c]);
+            }
+        }
+    }
+
+    return res;
+};
diff --git a/sum-of-two-integers/hsskey.js b/sum-of-two-integers/hsskey.js
new file mode 100644
index 000000000..13ac99cf1
--- /dev/null
+++ b/sum-of-two-integers/hsskey.js
@@ -0,0 +1,14 @@
+/**
+ * @param {number} a
+ * @param {number} b
+ * @return {number}
+ */
+var getSum = function(a, b) {
+    while (b !== 0) {
+        let carry = (a & b) << 1;
+        a = a ^ b;
+        b = carry;
+    }
+    return a;
+};
+