Description：
Given an array of integers and an integer k, find out whether there 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
public class Solution {
public boolean containsNearbyDuplicate(int[] nums, int k) {
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for(int i=0; i<nums.length; i++) {
if(map.containsKey(nums[i])) {
int j = map.get(nums[i]);
if(i-j<=k) {
return true;
}
else {
map.remove(nums[j]);
map.put(nums[i], i);
}
}
else {
map.put(nums[i], i);
}
}
return false;
}
}