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.

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

題意：判斷一個數組是否有重複的數，有返回true，無返回false

• hashset集合中不允許有重複的元素
• 建立：Set<資料型別> 集合名 = new HashSet<>(長度);
• 引入：import java.util.HashSet;
• 介面：boolean: add(E object),boolean: contains(Object object)

2、陣列foreach遍歷方式：for(int i : nums)

class Solution {
    public
 
 boolean containsDuplicate(int[] nums) {
        int len = nums.length;
        if(len>1){
            Set<Integer> set = new HashSet<>(len);//HashSet建立
            for(int i : nums){
                if(set.contains(i)){//如果set集合中有i元素，true
                    return true;
                }else
 
 {
                    set.add(i);//在set集合中新增i元素
                }
            }
        }
        return false;
    }
}