[LeetCode] Contains Duplicate

Question

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.

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本题难度Easy。

集合法

复杂度

时间 O(N) 空间 O(N)

思路

利用集合set对待处理数字num进行检测：如果set中含有该num，则返回true；否则，将该num放入set中。

代码

public class Solution {    public boolean containsDuplicate(int[] nums) {        //require        if(nums==null||nums.length<2)            return false;        Set<Integer> set = new HashSet<>();        //invariant        for(int num:nums)            if(set.contains(num))                return true;            else                set.add(num);        //ensure        return false;    }}