Difficulty:easy
More:【目录】LeetCode Java实现
Description
https://leetcode.com/problems/contains-duplicate-ii/
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 absolutedifference 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
Intuition
hashSet
Solution
public boolean containsNearbyDuplicate(int[] nums, int k) {
if(nums == null)
return false;
HashSet<Integer> set = new HashSet<>();
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;
}
Complexity
Time complexity : O(n)
Space complexity : O(k)
What I've learned
1. set.add(e) returns false if the set already contains the specified element.
More:【目录】LeetCode Java实现