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:

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

    Example 2:

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

    Example 3:

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

    题意

    判断给定数组中是否存在一组重复的数，它们的下标之差的绝对值不大于k。

    思路

    用Hash处理很简单。

    代码实现

    1. class Solution {
    2.     public boolean containsNearbyDuplicate(int[] nums, int k) {
    3.         Map<Integer, Integer> map = new HashMap<>();
    4.         for (int i = 0; i < nums.length; i++) {
    5.             if (i - map.getOrDefault(nums[i], -k - 1) <= k) {
    6.                 return true;
    7.             }
    8.             map.put(nums[i], i);
    9.         }
    10.         return false;
    11.     }
    12. }