字符串交叉输入，就是将一个字符串交叉的输入到了另一个字符串当中，比如：char a[4]= ABCD char b[4]= abcd 则char c[8]= AaBbCcDd-Cross-string input, is to cross a string input to another string of them, such as: char a [4] =　ABCD　 char b [4] =　abcd　 While char c [8] =　AaBbCcDd