问题描述
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.
思路：刚开始就用了双层for循环，超时了

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function(nums) {
    nums.sort();
    for(var i = 0; i < nums.length-1; i++){
        if(nums[i] == nums[i+1]){
            return true;
        }
    }
    return false;
};