Input:The first line is an integer n indicates the number of operations. Each of the next n lines is either “a x” or “r x” which indicates the operation is add or remove. Output:For each operation: If the o
--第一步:设置行索引SET@rowindex:=0;SELECTROUND(AVG(lat_n),4)FROM--第二步:内查询建立新的根据lat_n排好序的索引(SELECT@rowindex:=@rowindex+1ASrowindex,lat_nFROMstationORDERBYlat_n)ASS--第三步:外查询取中位数的平均值,具体解释如下WHERES.rowindexIN(FLOOR((@rowindex+1)/2),CEIL((@row...