r - 如何匹配不同的重复字符

Question

我试图在 R 中提出一个正则表达式来匹配重复两个不同字符的字符串。

x <- c("aaaaaaah" ,"aaaah","ahhhh","cooee","helloee","mmmm","noooo","ohhhh","oooaaah","ooooh","sshh","ummmmm","vroomm","whoopee","yippee")

此正则表达式匹配以上所有内容，包括诸如“mmmm”和“ohhhh”之类的字符串，其中第一次和第二次重复中的重复字母相同:

grep(".*([a-z])\\1.*([a-z])\\2", x, value = T)

我想匹配的内容 x这些字符串的重复字母是不同的:

"cooee","helloee","oooaaah","sshh","vroomm","whoopee","yippee"

如何调整正则表达式以确保第二个重复字符与第一个不同？

Answer 1

您可以使用 negative lookahead 限制第二个字符模式。 :

grep(".*([a-z])\\1.*(?!\\1)([a-z])\\2", x, value=TRUE, perl=TRUE)
#                    ^^^^^

见 regex demo .(?!\\1)([a-z])表示匹配并捕获与组 1 中的值不同的任何小写 ASCII 字母并将其捕获到组 2 中。
R demo :

x <- c("aaaaaaah" ,"aaaah","ahhhh","cooee","helloee","mmmm","noooo","ohhhh","oooaaah","ooooh","sshh","ummmmm","vroomm","whoopee","yippee")
grep(".*([a-z])\\1.*(?!\\1)([a-z])\\2", x, value=TRUE, perl=TRUE)
# => "cooee"   "helloee" "oooaaah" "sshh"    "vroomm"  "whoopee" "yippee"