解法：
1.Construct時先將停車位數量保存
2.判斷要停的車位為null，回傳false
3.停的車位存在則將其數量減1，回傳true
JavaScript
/**
* @param {number} big
* @param {number} medium
* @param {number} small
*/
var ParkingSystem = function (big, medium, small) {
this.c = [big, medium, small]
};
/**
* @param {number} carType
* @return {boolean}
*/
ParkingSystem.prototype.addCar = function (carType) {
if (!this.c[carType - 1])
return false;
--this.c[carType - 1];
return true;
};
/**
* Your ParkingSystem object will be instantiated and called as such:
* var obj = new ParkingSystem(big, medium, small)
* var param_1 = obj.addCar(carType)
*/