題目：

題解：

class Solution {public boolean containsNearbyDuplicate(int[] nums, int k) {Set<Integer> set = new HashSet<Integer>();int length = nums.length;for (int i = 0; i < length; i++) {if (i > k) {set.remove(nums[i - k - 1]);}if (!set.add(nums[i])) {return true;}}return false;}
}