冒泡排序法
  例如: for(i=0;i<scores.length-1;i++) //控制比较多少轮,scores是数组
        {
           for(j = 0 ;j<scores.length-1-i;j++)
           {
              if(scores[j]>scores[j+1])
              .........
                 //交换数直
            }

         }