217. Contains Duplicate

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.

解题思路：
先排序，再遍历数组前后两个元素，如果有相等的情况，返回true，否则返回false。

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