Leet Code OJ 219. Contains Duplicate II [Difficulty: Easy]

题目:
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 j is at most k.

翻译：
给定一个整数数组和一个整数k，找出是否存在下标i，j使得nums[i] = nums[j]，同时i，j的差值小于等于k。

分析：
遍历数组，使用map存储每个值最近一次出现的下标。

代码：

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