Contains Duplicate II(leetcode219)

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.

Example 1:

Input: nums = [1,2,3,1], k = 3
Output: true

Example 2:

Input: nums = [1,0,1,1], k = 1
Output: true

Example 3:

Input: nums = [1,2,3,1,2,3], k = 2
Output: false

实现：

public static boolean containsDuplicate2(int[] nums, int k) {
    Map<Integer,Integer> map = new HashMap();
    int tag=0;
    for(int i = 0;i< nums.length;i++){
        Integer value = map.get(nums[i]);
        if(null !=map.put(nums[i],i)){
            if((i-value) <= k){
               return true;
            }
        }
    }
    return false;
}

// 这里还直接用了删除的方法 保持在k的范围内
public static boolean containsNearbyDuplicate(int[] nums, int k) {
    Set<Integer> set = new HashSet<Integer>();
    for(int i = 0; i < nums.length; i++){
        if(i > k) {
            set.remove(nums[i-k-1]);
        }
        if(!set.add(nums[i])) {
            return true;
        }
    }
    return false;
}

git：https://github.com/woshiyexinjie/leetcode-xin