LeetCode 220. Contains Duplicate III

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最新推荐文章于 2025-03-13 00:08:53 发布

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220. Contains Duplicate III

Medium

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[j] is at most t and the absolute difference between i and j is at most k.

Example 1:

Input: nums = [1,2,3,1], k = 3, t = 0
Output: true
Example 2:

Input: nums = [1,0,1,1], k = 1, t = 2
Output: true
Example 3:

Input: nums = [1,5,9,1,5,9], k = 2, t = 3
Output: false

题意

给定一个数组和一个整数k, 一个整数t，判断数组中是否存在两个元素，满足其下标之差小于等于k且两数之差的绝对值小于等于t

思路

维护一个Java的TreeSet存储长度为k的滑动窗口，在其中查找与当前元素值绝对值之差小于等于t的元素
TreeSet底层采用红黑树实现，当TreeSet规模为N时，按指定值查询、删除、添加元素的复杂度均为O(logN)
涉及TreeSet的两个操作：(1)删除指定值的元素，(2)找到指定值的元素，复杂度均为O(logk)
算法总的时间复杂度为O(nlogk)，空间复杂度为O(k)

代码

class Solution {
    public boolean containsNearbyAlmostDuplicate(int[] nums, int k, int t) {
        TreeSet<Long> set = new TreeSet<Long>();
        int i = 0;
        for (int num: nums) {
            Long ceil = set.ceiling((long)(num) - (long)(t));
            if (ceil != null && ceil <= (long)(num) + (long)(t)){
                return true;
            }
            set.add((long)num);
            if (set.size() > k) {
                set.remove((long)nums[i - k]);
            }
            ++i;
        }
        return false;
    }
}