Contains Duplicate LT217

佚名 6年前 (2019-05-12) 随笔 2077人围观抢沙发百度已收录

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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Example 1:

Input: [1,2,3,1]
Output: true

Example 2:

Input: [1,2,3,4]
Output: false

Example 3:

Input: [1,1,1,3,3,4,3,2,4,2]
Output: true

Idea 1. HashMap(Set)

Time complexity: O(N)

Space complexity: O(N)

other ideas: bruteforce(for each element, scan the whole to see if there is the same value element), sort(compare each element with its neighbour).

 1 class Solution {
 2     public boolean containsDuplicate(int[] nums) {
 3        Set<Integer> cache = new HashSet<>();
 4         
 5         for(int num: nums) {
 6             if(cache.contains(num)) {
 7                 return true;
 8             }
 9             cache.add(num);
10         }
11         
12         return false;
13     }
14 }