Leetcode：219. Contains Duplicate II（JAVA）

【问题描述】

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and jis at most k.

【思路】

1、两层循环判断，复杂度为O（n2）

2、采用HashMap判断，key为数组元素，value为下标

【code】

public class Solution {    public boolean containsNearbyDuplicate(int[] nums, int k) {       HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();for (int i = 0; i < nums.length; i++) {if (map.containsKey(nums[i])) {if ((i-map.get(nums[i])) <= k ) {return true;}}map.put(nums[i], i);}return false;     }}