Question

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

Thinking:

  • Method:
    • 使用hashMap,键即为数字，值为该键上次出现的位置。
class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        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;
    }
}

二刷

class Solution {
    public boolean containsNearbyDuplicate(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        for(int i = 0; i < nums.length; i++){
            int cur = nums[i];
            if(map.containsKey(cur)){
                if(i - map.get(cur) <= k) return true;
            }
            map.put(cur, i);
        }
        return false;
    }
}