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 absolute difference between i and j is at most k.
1、HashMap最直接。
public class Solution { public boolean containsNearbyDuplicate(int[] nums, int k) { HashMap<Integer, Integer> map = new HashMap(); for (int i = 0; i < nums.length; i++){ if (map.containsKey(nums[i])){ if (i - map.get(nums[i]) <= k){ return true; } } map.put(nums[i], i); } return false; } }
2、用HashSet也可以,用窗口的想法来实现。
public class Solution { public boolean containsNearbyDuplicate(int[] nums, int k) { HashSet<Integer> set = new HashSet(); for (int i = 0; i <= k && i < nums.length; i++){ if (set.contains(nums[i])){ return true; } set.add(nums[i]); } for (int i = k + 1, j = 0; i < nums.length; i++, j++){ set.remove(nums[j]); if (set.contains(nums[i])){ return true; } set.add(nums[i]); } return false; } }
可以对上面的代码简化一下。