add solution(s)

src/leetcode_23/n382_linked_list_random_node/Solution.java

@@ -0,0 +1,42 @@
+package n382_linked_list_random_node;
+
+import util.ListNode;
+
+public class Solution {
+  private final ListNode root;
+  private int size = 0;
+
+  public Solution(ListNode head) {
+    this.root = head;
+    while (head!=null) {size++;head = head.next;}
+  }
+
+  public int getRandom() {
+    var rnd = Math.random();
+    var res = root;
+    int nIdx = (int)Math.ceil(size * rnd) - 1;
+    for (int i = 0; i < nIdx; i++) res = res.next;
+    return res.val;
+  }
+
+  public int getRandomSlowCorrect() {
+    var rnd = Math.random();
+    var iter = root;
+    var res = root;
+    int size = 1, lastIdx= 1;
+    while (iter != null) {
+      int nIdx = (int)Math.ceil(size * rnd);
+      if (lastIdx< nIdx) {res = res.next!=null ? res.next : res;lastIdx =nIdx;}
+      size++;
+      iter = iter.next;
+    }
+    return res.val;
+  }
+
+  public static void main(String[] args) {
+    var s = new Solution(ListNode.of(1, 2, 3));
+    for (int i = 0; i < 3; i++) {
+      System.out.println(s.getRandom());
+    }
+  }
+}

src/leetcode_23/n502_ipo/Solution.java

@@ -1,7 +1,5 @@
 package n502_ipo;
 
-import scala.Int;
-
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.PriorityQueue;