Linked List Random Node LeetCode solution in Java

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class Solution {
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  int N = 0;
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  ListNode head = null;
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  public Solution(ListNode head) {
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    this.head = head;
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  }
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  public int getRandom() {
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    ListNode p = this.head;
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    int i = 1, ans = 0;
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    while (p != null) {
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      if (Math.random() * i < 1) ans = p.val; // replace ans with i-th node.val with probability 1/i
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      p = p.next;
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      i++;
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    }
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    return ans;
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  }
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}