最优合并问题,当取最小值保证每次的2个加数为最小便可，最大值同理取当前最大的两个值便可。取最小值与取最大值实现的方式不同，最小值不需要排序。-Optimal merger, when the minimum value of each guaranteed two addends can be minimum, maximum empathy take the current maximum of two values can be. Take the minimum and maximum value achieved in different ways, it does not require minimum order.