(easy)LeetCode 219.Contains Duplicate II

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 iand j is at most k.

方法1：暴力解法

代码如下：

public class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
      int len=nums.length;
      for(int i=0;i<len;i++){
          for(int tmp=1;tmp<=k && i+tmp<len;tmp++)
              if(nums[i]==nums[i+tmp])
                 return true;
      }
      return false;

    }
}

　　运行超时：

方法2：分析：

代码如下：

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

    }
}

　运行结果：