219. Contains Duplicate II

Given an array of integers and an integer k, find out whether there are two distinct indicesi andj in the array such thatnums[i] = nums[j] and the difference betweeni andj is at mostk.

public boolean containsNearbyDuplicate(int[] nums, int k) {
if (nums == null || nums.length <= 1 || k <= 0)
return false;
Map map = new HashMap();
for (int i = 0; i < nums.length; i++) {
if (map.containsKey(nums[i])) {
int preIndex = (int) map.get(nums[i]);
if (i - preIndex <= k)
return true;
}
map.put(nums[i], i);
}
return false;
}