linked-list-random-node.rs

#![allow(dead_code, unused, unused_variables)]

use rand::Rng;

fnmain(){}

// Definition for singly-linked list.
#[derive(PartialEq,Eq,Clone,Debug)]
pubstructListNode{
pubval:i32,
pubnext:Option<Box<ListNode>>,
}

implListNode{
#[inline]
fnnew(val:i32) -> Self{
ListNode{next:None, val }
}
}

/**
 * Your Solution object will be instantiated and called as such:
 * let obj = Solution::new(head);
 * let ret_1: i32 = obj.get_random();
 */
structSolution{
head:Option<Box<ListNode>>,
}

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
implSolution{
/** @param head The linked list's head.
 Note that the head is guaranteed to be not null, so it contains at least one node. */
fnnew(head:Option<Box<ListNode>>) -> Self{
Self{ head }
}

/** Returns a random node's value. */
fnget_random(&self) -> i32{
use rand::Rng;
letmut s = &self.head;
letmut n = 1;
letmut r = 0;
whileletSome(x) = s {
if rand::thread_rng().gen_range(0..n) == 0{
 r = x.val;
}

 s = &x.next;
 n += 1;
}
 r
}
}