题目描述：
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 j is at most k.
解题思路：
HashMap解决。
代码如下：
public class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
Map<Integer,Integer> map = new HashMap<Integer,Integer>();
int len = nums.length;
if(nums == null || len == 0)
return false;
for(int i = 0; i < len; i++){
if(!map.containsKey(nums[i]))
map.put(nums[i], i);
else {
if(i - map.get(nums[i]) <= k)
return true;
else
map.put(nums[i], i);
}
}
return false;
}
}