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

分析：

判斷陣列中是否含重複元素。可以先對陣列中的元素進行排序，再依次遍歷陣列，若存在相鄰元素相等，直接返回true，否則返回false。

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        int len = nums.size();
        sort(nums.begin() , nums.end());
        for(int i=0; i<len-1; i++)
        {
            if(nums[i] == nums[i+1])
                return true;
        }
        return false;
    }
};