Improved java.util.Random

Author: javadev

src/main/kotlin/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSet.kt

@@ -3,17 +3,15 @@ package g0301_0400.s0380_insert_delete_getrandom_o1
 // #Medium #Top_Interview_Questions #Array #Hash_Table #Math #Design #Randomized
 // #Programming_Skills_II_Day_20 #2022_11_22_Time_1326_ms_(68.23%)_Space_119.7_MB_(83.53%)
 
-import java.util.Random
+import kotlin.random.Random
 
 @Suppress("kotlin:S2245")
 class RandomizedSet {
-    private val rand: Random
     private val list: MutableList<Int>
     private val map: MutableMap<Int, Int>
 
     /* Initialize your data structure here. */
     init {
-        rand = Random()
         list = ArrayList()
         map = HashMap()
     }
@@ -45,7 +43,7 @@ class RandomizedSet {
 
     /* Get a random element from the set. */
     fun getRandom(): Int {
-        return list[rand.nextInt(list.size)]
+        return list[Random.nextInt(list.size)]
     }
 }
 

src/main/kotlin/g0301_0400/s0382_linked_list_random_node/Solution.kt

@@ -4,7 +4,7 @@ package g0301_0400.s0382_linked_list_random_node
 // #2022_11_24_Time_283_ms_(100.00%)_Space_38.6_MB_(100.00%)
 
 import com_github_leetcode.ListNode
-import java.util.Random
+import kotlin.random.Random
 
 /*
  * Example:
@@ -18,12 +18,10 @@ import java.util.Random
 @Suppress("NAME_SHADOWING", "kotlin:S2245")
 class Solution(head: ListNode?) {
     private val al: MutableList<Int>
-    private val rand: Random
 
     init {
         var head = head
         al = ArrayList()
-        rand = Random()
         while (head != null) {
             al.add(head.`val`)
             head = head.next
@@ -37,7 +35,7 @@ class Solution(head: ListNode?) {
         take only the integer part which is a random index.
         return the element at that random index.
          */
-        val ind = rand.nextInt(al.size)
+        val ind = Random.nextInt(al.size)
         return al[ind]
     }
 }

src/main/kotlin/g0301_0400/s0384_shuffle_an_array/Solution.kt

@@ -3,12 +3,10 @@ package g0301_0400.s0384_shuffle_an_array
 // #Medium #Top_Interview_Questions #Array #Math #Randomized #Algorithm_II_Day_20_Others
 // #2022_11_24_Time_940_ms_(72.09%)_Space_81.5_MB_(51.16%)
 
-import java.util.Random
+import kotlin.random.Random
 
 @Suppress("kotlin:S2245")
 class Solution(private val nums: IntArray) {
-    private val random: Random = Random()
-
     // Resets the array to its original configuration and return it.
     fun reset(): IntArray {
         return nums
@@ -18,7 +16,7 @@ class Solution(private val nums: IntArray) {
     fun shuffle(): IntArray {
         val shuffled = nums.clone()
         for (i in nums.size - 1 downTo 1) {
-            val j: Int = random.nextInt(i + 1)
+            val j: Int = Random.nextInt(i + 1)
             swap(shuffled, i, j)
         }
         return shuffled

src/main/kotlin/g0301_0400/s0398_random_pick_index/Solution.kt

@@ -3,17 +3,15 @@ package g0301_0400.s0398_random_pick_index
 // #Medium #Hash_Table #Math #Randomized #Reservoir_Sampling
 // #2022_11_29_Time_1091_ms_(75.00%)_Space_84.3_MB_(25.00%)
 
-import java.util.Random
+import kotlin.random.Random
 
 @Suppress("kotlin:S2245")
 class Solution(nums: IntArray) {
     // O(n) time | O(n) space
     private val map: MutableMap<Int, MutableList<Int>>
-    private val rand: Random
 
     init {
         map = HashMap()
-        rand = Random()
         for (i in nums.indices) {
             map.computeIfAbsent(
                 nums[i]
@@ -23,7 +21,7 @@ class Solution(nums: IntArray) {
 
     fun pick(target: Int): Int {
         val list: List<Int> = map[target]!!
-        return list[rand.nextInt(list.size)]
+        return list[Random.nextInt(list.size)]
     }
 }