219.contains-duplicate-ii.java

/*
 * @lc app=leetcode id=219 lang=java
 *
 * [219] Contains Duplicate II
 *
 * https://leetcode.com/problems/contains-duplicate-ii/description/
 *
 * algorithms
 * Easy (34.71%)
 * Likes:    503
 * Dislikes: 620
 * Total Accepted:    202.3K
 * Total Submissions: 570.3K
 * Testcase Example:  '[1,2,3,1]\n3'
 *
 * 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
 *
 *
 *
 *
 *
 */
class Solution {
  public boolean containsNearbyDuplicate(int[] nums, int k) {
    if (nums == null) {
      return false;
    }

    Map<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;
  }
}