Colin enjoys chatting with Eva online, but he felt that typing with a traditional keyboard was too tiring, so he bought a new keyboard, as shown in the figure below, leaving only the two keys he really needed: Copy and Paste.Assuming a string SSS is displayed on the current screen, then :. If you press Copy,then the current string SSS will be copied entirelyinto memory and stored as another string called TTT .If you press Paste, then the system will concatenate the stringTTT after SSS, which means the string displayed on the screen will become S+TS+TS+T . If no Copy has been executed before, then TTT is an empty string.Although the keyboard is already simple enough, Colin still finds it too tiring to think about how to use these two keys. So he decide to use them in turn: At first, press Copy, then Paste, then Copy, then Paste, taking turns until the string displayed on the screen is the one he wants.Assuming that there is now a string S1S_1S1 on the screen, and no operation has been executed before , can Colin obtain the string S2S_2S2 he wants through the above operations?
Colin enjoys chatting with Eva online, but he felt that typing with a traditional keyboard was too tiring, so he bought a new keyboard, as shown in the figure below, leaving only the two keys he really needed: Copy and Paste. Assuming a string SSS is displayed on the current screen, then (Note that this is different from a regular keyboard) : If you press Copy, then the current string SSS will be copied entirely into memory and stored as another string called TTT . If you press Paste, then the system will concatenate the string TTT after SSS, which means the string displayed on the screen will become S+TS+TS+T (string connection) . If no Copy has been executed before, then TTT is an empty string. Although the keyboard is already simple enough, Colin still finds it too tiring to think about how to use these two keys. So he decide to use them in turn: At first, press Copy, then Paste, then Copy, then Paste, taking turns until the string displayed on the screen is the one he wants. Assuming that there is now a string S1S_1S1 on the screen, and no operation has been executed before (TTT is an empty string), can Colin obtain the string S2S_2S2 he wants through the above operations?
