[gmlwls96] Week1

contains-duplicate/gmlwls96.kt

@@ -0,0 +1,7 @@
+package leetcode_study
+
+class Solution {
+    fun containsDuplicate(nums: IntArray): Boolean {
+        return nums.toSet().size != nums.size
+    }
+}

house-robber/gmlwls96.kt

@@ -0,0 +1,16 @@
+package leetcode_study
+
+import java.lang.Integer.max
+
+class Solution {
+    fun rob(nums: IntArray): Int {
+        return max(rob_recursion(nums, 0), rob_recursion(nums, 1))
+    }
+
+    private fun rob_recursion(nums: IntArray, index: Int): Int {
+        if (index >= nums.size) {
+            return 0
+        }
+        return nums[index] + Integer.max(rob_recursion(nums, index + 2), rob_recursion(nums, index + 3))
+    }
+}

longest-consecutive-sequence/gmlwls96.kt

@@ -0,0 +1,18 @@
+package leetcode_study
+
+class Solution {
+    fun longestConsecutive(nums: IntArray): Int {
+        nums.sort()
+        val consecutiveArray = IntArray(nums.size)
+        var maxCount = 0
+        for (i in nums.lastIndex - 1 downTo (0)) {
+            if (nums[i] + 1 == nums[i + 1]) {
+                consecutiveArray[i] += consecutiveArray[i + 1] + 1
+                if (consecutiveArray[i] > maxCount) {
+                    maxCount = consecutiveArray[i]
+                }
+            }
+        }
+        return maxCount + 1
+    }
+}

top-k-frequent-elements/gmlwls96.kt

@@ -0,0 +1,15 @@
+class Solution {
+    fun topKFrequent(nums: IntArray, k: Int): IntArray {
+        val answer = IntArray(k)
+        val set = nums.toSet()
+        val mutableList = mutableListOf<Pair<Int, Int>>()
+        set.forEach { num ->
+            mutableList.add(num to nums.count { it == num })
+        }
+        mutableList.sortByDescending { it.second }
+        for (i in 0 until k) {
+            answer[i] = mutableList[i].first
+        }
+        return answer
+    }
+}

valid-palindrome/gmlwls96.kt

@@ -0,0 +1,12 @@
+class Solution {
+    fun isPalindrome(s: String): Boolean {
+        val filterStr = s
+            .lowercase()
+            .filter { it in 'a'..'z' }
+        if (filterStr.isEmpty()) return true
+        for (i in 0..filterStr.lastIndex / 2) {
+            if (filterStr[i] != filterStr[filterStr.lastIndex - i]) return false
+        }
+        return true
+    }
+}