219.Contains-Duplicate-II

219. Contains Duplicate II

题目地址

https://leetcode.com/problems/contains-duplicate-ii/

题目描述

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

代码

Approach #1 Naive Linear Search

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

Approach #2 (Hash Table)

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