若已知一个栈的入栈序列是1,2,3,…,n，其输出序列为p1,p2,p3,…,pn，若p1=n，则pi为n-i+1。
A child who has once been pleased with a tale likes, as a rule, to have it retold in almost the same words, but this should not lead parents to treat printed fairy stories as formal texts. It is always much better to tell a story than read it out of a book, and, if a parent can produce what, in the actual situation of the time and the child, is an improvement on the printed text, so much the better. A charge made against fairy tales is that they harm the child by frightening him or making him sad thinking. To prove the latter, one would have to show in a controlled experiment that children who have read fairy stories were more often sorry for cruelty than those who had not. As to fears, there are, I think, some cases of children being dangerously terrified by some fairy story. Often, however, this arises (出现) from the child having heard the story once. Familiarity with the story by repetition turns the pain of fear into the pleasure of a fear faced and mastered.There are also people who object to fairy stories on the grounds that they are not objectively true, that giants, witches, twoheaded dragons, magic carpets, etc. do not exist; and that, instead of being fond of the strange side in fairy tales, the child should be taught to learn the reality by studying history. I find such people, I must say so peculiar (奇怪的) that I do not know how to argue with them. If their case were sound, the world should be full of mad men attempting to fly from New York to Philadelphia on a stick or covering a telephone with kisses in the belief that it was their beloved girlfriend. No fairy story ever declared to be a description of the real world and no clever child has ever believed that it was.4.Theauthor’smentionofsticksandtelephonesismeanttosuggestthat_______.