diff --git a/oh-chaeyeon/139_Word_Break.js b/oh-chaeyeon/139_Word_Break.js
new file mode 100644
index 0000000..022de5f
--- /dev/null
+++ b/oh-chaeyeon/139_Word_Break.js
@@ -0,0 +1,30 @@
+/**
+ * @param {string} s
+ * @param {string[]} wordDict
+ * @return {boolean}
+ */
+var wordBreak = function (s, wordDict) {
+  const wordSet = new Set(wordDict);
+  const dp = new Array(s.length + 1).fill(false);
+  dp[0] = true;
+
+  for (let i = 1; i <= s.length; i++) {
+    for (const word of wordSet) {
+      const wordLength = word.length;
+      if (
+        i >= wordLength &&
+        dp[i - wordLength] &&
+        s.substring(i - wordLength, i) === word
+      ) {
+        dp[i] = true;
+        break;
+      }
+    }
+  }
+
+  return dp[s.length];
+};
+
+// Time taken : 12m 49s
+// Runtime : 3ms
+// Memory : 51.24MB
diff --git a/oh-chaeyeon/1584_Min_Cost_to_Connect_all_points.js b/oh-chaeyeon/1584_Min_Cost_to_Connect_all_points.js
new file mode 100644
index 0000000..7ca304b
--- /dev/null
+++ b/oh-chaeyeon/1584_Min_Cost_to_Connect_all_points.js
@@ -0,0 +1,41 @@
+/**
+ * @param {number[][]} points
+ * @return {number}
+ */
+var minCostConnectPoints = function (points) {
+  const n = points.length;
+  const dist = new Array(n).fill(Infinity);
+  const visited = new Array(n).fill(false);
+  dist[0] = 0;
+  let cost = 0;
+
+  for (let i = 0; i < n; i++) {
+    let minCost = Infinity;
+    let currentNode = -1;
+
+    for (let j = 0; j < n; j++) {
+      if (!visited[j] && dist[j] < minCost) {
+        minCost = dist[j];
+        currentNode = j;
+      }
+    }
+
+    visited[currentNode] = true;
+    cost += minCost;
+
+    for (let nextNode = 0; nextNode < n; nextNode++) {
+      if (!visited[nextNode]) {
+        const manhattanDistance =
+          Math.abs(points[currentNode][0] - points[nextNode][0]) +
+          Math.abs(points[currentNode][1] - points[nextNode][1]);
+        dist[nextNode] = Math.min(dist[nextNode], manhattanDistance);
+      }
+    }
+  }
+
+  return cost;
+};
+
+// Time taken : 1h+
+// Runtime : 33ms
+// Memory : 52.37MB
diff --git a/oh-chaeyeon/215_Kth largest_element_in_an_Array.js b/oh-chaeyeon/215_Kth largest_element_in_an_Array.js
new file mode 100644
index 0000000..01dc25a
--- /dev/null
+++ b/oh-chaeyeon/215_Kth largest_element_in_an_Array.js	
@@ -0,0 +1,46 @@
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+var findKthLargest = function (nums, k) {
+  const maxHeap = new MaxPriorityQueue();
+
+  for (const num of nums) {
+    maxHeap.enqueue(num);
+  }
+
+  for (let i = 0; i < k - 1; i++) {
+    maxHeap.dequeue();
+  }
+  return maxHeap.front().element;
+};
+
+// Time taken : 16m 50s
+// Runtime : 148ms
+// Memory : 77.60MB
+
+//----------------------------------------------------
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+var findKthLargest = function (nums, k) {
+  const offset = 10000;
+  const count = new Array(20001).fill(0);
+
+  for (let num of nums) {
+    count[num + offset]++;
+  }
+
+  let total = 0;
+  for (let i = count.length - 1; i >= 0; i--) {
+    total += count[i];
+    if (total >= k) return i - offset;
+  }
+};
+
+// Runtime : 5ms
+// Memory : 58.40MB
diff --git a/oh-chaeyeon/235_Lowest_Common_ancestor_of_a_Binary_Search_Tree.js b/oh-chaeyeon/235_Lowest_Common_ancestor_of_a_Binary_Search_Tree.js
new file mode 100644
index 0000000..32182d3
--- /dev/null
+++ b/oh-chaeyeon/235_Lowest_Common_ancestor_of_a_Binary_Search_Tree.js
@@ -0,0 +1,30 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+
+/**
+ * @param {TreeNode} root
+ * @param {TreeNode} p
+ * @param {TreeNode} q
+ * @return {TreeNode}
+ */
+var lowestCommonAncestor = function (root, p, q) {
+  while (root) {
+    if (p.val < root.val && q.val < root.val) {
+      root = root.left;
+    } else if (p.val > root.val && q.val > root.val) {
+      root = root.right;
+    } else {
+      return root;
+    }
+  }
+  return null;
+};
+
+// Time taken : 9m 37s
+// Runtime : 56ms
+// Memory : 58.70MB
diff --git a/oh-chaeyeon/56_Merge_Intervals.js b/oh-chaeyeon/56_Merge_Intervals.js
new file mode 100644
index 0000000..5b518dd
--- /dev/null
+++ b/oh-chaeyeon/56_Merge_Intervals.js
@@ -0,0 +1,29 @@
+/**
+ * @param {number[][]} intervals
+ * @return {number[][]}
+ */
+var merge = function (intervals) {
+  if (intervals.length === 0) return [];
+  intervals.sort((a, b) => a[0] - b[0]);
+
+  const merged = [intervals[0]];
+
+  for (let i = 1; i < intervals.length; i++) {
+    const current = intervals[i];
+
+    if (current[0] <= merged[merged.length - 1][1]) {
+      merged[merged.length - 1][1] = Math.max(
+        merged[merged.length - 1][1],
+        current[1]
+      );
+    } else {
+      merged.push(current);
+    }
+  }
+
+  return merged;
+};
+
+// Time taken : 23m 25s
+// Runtime : 7ms
+// Memory : 59.04MB