LeetCode-Go/leetcode/0382.Linked-List-Random-Node/382. Linked List Random Node.go

package leetcode

import (
	"math/rand"

	"github.com/halfrost/LeetCode-Go/structures"
)

// ListNode define
type ListNode = structures.ListNode

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
type Solution struct {
	head *ListNode
}

/** @param head The linked list's head.
  Note that the head is guaranteed to be not null, so it contains at least one node. */
func Constructor(head *ListNode) Solution {
	return Solution{head: head}
}

/** Returns a random node's value. */
func (this *Solution) GetRandom() int {
	scope, selectPoint, curr := 1, 0, this.head
	for curr != nil {
		if rand.Float64() < 1.0/float64(scope) {
			selectPoint = curr.Val
		}
		scope += 1
		curr = curr.Next
	}
	return selectPoint
}

/**
 * Your Solution object will be instantiated and called as such:
 * obj := Constructor(head);
 * param_1 := obj.GetRandom();
 */