diff --git a/kotlin/153-Find-Minimum-In-Rotated-Sorted-Array.kt b/kotlin/153-Find-Minimum-In-Rotated-Sorted-Array.kt
new file mode 100644
index 000000000..6049f7a6b
--- /dev/null
+++ b/kotlin/153-Find-Minimum-In-Rotated-Sorted-Array.kt
@@ -0,0 +1,19 @@
+class Solution {
+    fun findMin(nums: IntArray): Int {
+        val n = nums.size
+        if(n == 1) return nums[0]
+        var low = 0
+        var high = n - 1
+        var min = Int.MIN_VALUE
+        while(low < high) {
+            var mid = low + (high - low)/2
+            if(nums[mid] < nums[high]) {
+                high = mid
+            } else {
+                low = mid + 1
+            }
+            min = nums[low]
+        }
+        return min
+    }
+}
\ No newline at end of file
diff --git a/kotlin/239-Sliding-Window-Maximum.kt b/kotlin/239-Sliding-Window-Maximum.kt
new file mode 100644
index 000000000..cf0d5feca
--- /dev/null
+++ b/kotlin/239-Sliding-Window-Maximum.kt
@@ -0,0 +1,38 @@
+class Solution {
+	fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+		if (nums.isEmpty() || k == 0) {
+			return intArrayOf()
+		}
+		var i = 0
+		val queue = arrayListOf<Int>()
+		val array = IntArray(nums.size - k + 1)
+		var slideIndex = 0
+
+		while (i < nums.size) {
+			/**
+			 * remove head if it is out of range of the sliding window
+			 */
+			if (queue.isNotEmpty() && i - queue[0] == k) {
+				queue.removeAt(0)
+			}
+
+			/**
+			 * remove from the tail if it's smaller than nums[i]
+			 */
+			var j = queue.size - 1
+			while (queue.isNotEmpty() && j >= 0 && nums[queue[j]] < nums[i]) {
+				queue.removeAt(queue.size - 1)
+				j --
+			}
+
+			queue.add(i)
+			if (i - k + 1 >= 0) {
+				array[slideIndex ++] = nums[queue[0]]
+			}
+
+			i++
+		}
+
+		return array
+	}
+}
\ No newline at end of file
diff --git a/kotlin/4-Median-Of-Two-Sorted-Arrays.kt b/kotlin/4-Median-Of-Two-Sorted-Arrays.kt
new file mode 100644
index 000000000..2cd9644a1
--- /dev/null
+++ b/kotlin/4-Median-Of-Two-Sorted-Arrays.kt
@@ -0,0 +1,14 @@
+class Solution {
+    fun findMedianSortedArrays(nums1: IntArray, nums2: IntArray): Double {
+        var i1 = 0
+        var i2 = 0
+        fun getNext() = when {
+            i1 < nums1.size && i2 < nums2.size -> if (nums1[i1] < nums2[i2]) nums1[i1++] else nums2[i2++]
+            i1 < nums1.size -> nums1[i1++]
+            else -> nums2[i2++]
+        }
+        val arr = IntArray(nums1.size + nums2.size) { getNext() }
+        return if (arr.size % 2 == 1) arr[arr.size / 2].toDouble()
+        else  (arr[arr.size / 2] + arr[arr.size / 2 - 1]) / 2.0
+    }
+}
\ No newline at end of file