398. Random Pick Index
Posted andywu
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了398. Random Pick Index相关的知识,希望对你有一定的参考价值。
Given an array of integers with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array.
Note:
The array size can be very large. Solution that uses too much extra space will not pass the judge.
Example:
int[] nums = new int[] {1,2,3,3,3}; Solution solution = new Solution(nums); // pick(3) should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning. solution.pick(3); // pick(1) should return 0. Since in the array only nums[0] is equal to 1. solution.pick(1);
含义:给定一个可能包含重复元素的整数数组,给定一个目标数,随机输出其下标。你可以假设给定的目标数一定存在于数组中。
注意:数组长度可能很大。使用较多额外空间的解决方案无法通过系统测试。
1 class Solution { 2 3 private int[] nums; 4 public Solution(int[] nums) { 5 this.nums = nums; 6 } 7 8 public int pick(int target) { 9 Random r = new Random(); 10 ArrayList<Integer> idxs = new ArrayList<Integer>(); 11 for(int i=0;i<nums.length;i++){ 12 if(target==nums[i]){ 13 idxs.add(i); 14 } 15 } 16 return idxs.get(r.nextInt(idxs.size())); 17 } 18 } 19 20 /** 21 * Your Solution object will be instantiated and called as such: 22 * Solution obj = new Solution(nums); 23 * int param_1 = obj.pick(target); 24 */
以上是关于398. Random Pick Index的主要内容,如果未能解决你的问题,请参考以下文章