Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen.

What if the linked list is extremely large and its length is unknown to you? Could you solve this efficiently without using extra space?

Example:

``````// Init a singly linked list [1,2,3].

// getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning.
solution.getRandom();
``````
``````public class Solution {
private int[] nums;
private Random random;

public Solution(int[] nums) {
this.nums = nums;
this.random = new Random();
}

public int pick(int target) {
int result = -1;
int count = 0;

for (int i = 0; i < nums.length; i++) {
if (nums[i] != target) {
continue;
}
count++;

if (random.nextInt(count) == 0) {
result = i;
}
}

return result;
}
}

/**
* Your Solution object will be instantiated and called as such:
* Solution obj = new Solution(nums);
* int param_1 = obj.pick(target);
*/
``````

Hope this helps,
Michael 