function PriorityQueue () {
    this.collection = [];
    this.printCollection = function() {
      console.log(this.collection);
    };
    // Only change code below this line
    this.enqueue = function(arr){
        this.collection.unshift(arr);
    };
    
    this.dequeue = function(){
        // 最小元素的位置
        var minIndex = this.collection.length - 1, maxPri;
        for(var i = 0; i < this.collection.length; i++){
            if(i === 0){
                maxPri = this.collection[i][1];
            }else{
                if(maxPri >= this.collection[i][1]){
                    maxPri = this.collection[i][1];
                    minIndex = i;
                }
            }
        }
        var itemValue = this.collection[minIndex][0];
        this.collection.splice(minIndex, 1);
        return itemValue;
        
    };
    
    this.size = function(){
        return this.collection.length;
    };
    
    this.isEmpty = function(){
        return this.collection.length === 0 ? true : false;
    };
    
    
    // Only change code above this line
}