Leetcode Contains Duplicate II

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：

想到了一种结构map, key 是该值，value是该值对应的前一个index.

Java code:

public boolean containsNearbyDuplicate(int[] nums, int k) {
Map<Integer, Integer> values = new HashMap<Integer, Integer>(); //first is value, second is current index
for(int i = 0; i< nums.length; i++){
if(values.containsKey(nums[i])){
int x = values.get(nums[i]);
if((i-x) <= k) {
return true;
}
}
values.put(nums[i], i);
}
return false;
}