do while he while

do-while循环和while循环是两种不同的循环结构。它们都用于控制程序的循环执行，但在执行顺序和条件判断上有所不同。

do-while循环首先执行循环体中的代码，然后再进行条件判断。也就是说，无论条件是否满足，循环体中的代码至少会执行一次。当条件满足时，继续执行循环体，直到条件不满足为止。

而while循环首先进行条件判断，如果条件满足，则执行循环体中的代码。如果条件不满足，则直接跳过循环体，不执行其中的代码。

总结一下，do-while循环是先执行循环体，再判断条件；而while循环是先判断条件，再执行循环体。

在编程中，可以根据具体情况选择do-while循环或while循环来实现不同的功能。当循环体中的代码至少需要执行一次时，可以使用do-while循环。当循环的执行次数不确定时，可以使用while循环。

相关问题

38.He took his umbrella ______ it should rain.（2分） A in case of B in case C for fear D in time 39.Not until this term （ ） to realize how important this subject is to his future career as a diplomat.（2分） A he began B did he begin C he has begun D that he has begun 40.Great changes ______ in Shanghai since the beginning of the reform and opening-up policy.（2分） A took place B has taken place C has been taken place D have taken place 41.The larger the house is, ______.（2分） A the higher rent it is B the higher rent it would have C the higher the rent is D the higher rent it would be 42.Every time Jane has trouble ______ her car started, Sean will show up to lend a hand.（2分） A get B getting C to getting D to get44.Some bookshelves have been moved out of this office to make ______ for more computers.（2分） A space B place C room D position46. Wendy: Have you been to the new bakery on the corner? Arthur: NO, how is it? Wendy: It is heaven！________! （2分） A Their cakes are to strive for B Their cakes are to pay for C Their cakes are to struggle for D Their cakes are to die for 47.Dr. Jones, many students want to see you.（ ） they wait here or outside?（2分） A Do B Will C Shall D Would 48.（ ） who would like to go on the trip should put their names on the list. （2分） A Those B These C Somebody D The ones 49. Kate: Do you mind opening the door for me? Bob: _________. （2分） A It’s nothing B That’s all right C Yes, I’ll do it D Not at all 50.They first stop at a board _____ the menu is displayed.（2分） A when B while C where D which

38. B in case
39. B did he begin
40. D have taken place
41. C the higher the rent is
42. B getting
44. A space
46. D Their cakes are to die for
47. A Do
48. A Those
49. D Not at all
50. C where

A string consisting of lowercase English letters, (, and ) is said to be a good string if you can make it an empty string by the following procedure: First, remove all lowercase English letters. Then, repeatedly remove consecutive () while possible. For example, ((a)ba) is a good string, because removing all lowercase English letters yields (()), from which we can remove consecutive () at the 2-nd and 3-rd characters to obtain (), which in turn ends up in an empty string. You are given a good string S. We denote by S i ​ the i-th character of S. For each lowercase English letter a, b, …, and z, we have a ball with the letter written on it. Additionally, we have an empty box. For each i=1,2, … ,∣S∣ in this order, Takahashi performs the following operation unless he faints. If S i ​ is a lowercase English letter, put the ball with the letter written on it into the box. If the ball is already in the box, he faints. If S i ​ is (, do nothing. If S i ​ is ), take the maximum integer j less than i such that the j-th through i-th characters of S form a good string. (We can prove that such an integer j always exists.) Take out from the box all the balls that he has put in the j-th through i-th operations. Determine if Takahashi can complete the sequence of operations without fainting.用cpp解决

这道题的意思是，给定一个字符串S，S是一个好的字符串，如果您可以通过以下过程将其转换为空字符串：首先，删除所有小写英文字母。然后，反复删除连续的()，直到不可能为止。例如，((a)ba)是一个好的字符串，因为删除所有小写英文字母后得到(())，从中我们可以在第2和第3个字符处删除连续的()以获得()，而后者最终变为空字符串。您将得到一个好的字符串S。我们用S i 表示S的第i个字符。对于小写英文字母a，b，…和z，我们都有一个写有该字母的小球。另外，我们有一个空盒子。对于按此顺序的i=1,2,…,|S|，高桥除非他昏倒，否则执行以下操作。如果S i 是小写英文字母，将写有该字母的球放入盒子中。如果球已经在盒子中，他就会昏倒。如果S i 是(，则什么也不做。如果S i 是)，则取出最大的整数j，使得S的第j到第i个字符形成一个好的字符串。 （我们可以证明这样的整数j总是存在的。）从第j次到第i次