[LeetCode 217] Contains Duplicate

最新推荐文章于 2025-11-24 01:23:29 发布

原创最新推荐文章于 2025-11-24 01:23:29 发布 · 446 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#leetcode #hashmap

Leetcode 同时被 2 个专栏收录

287 篇文章

订阅专栏

Java

106 篇文章

订阅专栏

本文介绍了一种使用哈希映射来快速判断数组中是否存在重复元素的方法，复杂度为O(n)。

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Solution:

Can use hashmap to count frequence of each element.

O(n)

public boolean containsDuplicate(int[] nums) {
        int len = nums.length;
        if(len <= 1) return false;
        Map<Integer, Integer> count = new HashMap<>();
        for(int i = 0;i < len; i++) {
            if(count.containsKey(nums[i])) {
                if(count.get(nums[i]) == 1) return true;
            }
            count.put(nums[i], 1);
        }
        return false;
    }