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/*

* Question:

* 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.

*

* 注释： 判断一个数组是否有重复元素，如果重复则返回true,反之返回false

*

* Runtime: 136 ms

*/

/**

* @param {number[]} nums

* @return {boolean}

*/

var containsDuplicate = function(nums) {

var tempHash = {};

var i = nums.length -1;

var isDistinct = false;

//注意空数组情况，倒序提高速度

while (0 <= i){

if (!tempHash[nums[i]]){

tempHash[nums[i]] = true;

} else {

isDistinct = true;

}

i--;

}

return isDistinct;

};