使用現代正規表示式風格，如PCRE/PHP、Perl、.NET 或類似的，可以確定如果ASCII「影像」中存在由三個X 組成的垂直線。
考慮以下正規表示式：
(?xm) # ignore comments and whitespace, ^ matches beginning of line
^ # beginning of line
(?:
. # any character except \n
(?= # lookahead
.*+\n # go to next line
( ?+ . ) # add a character to the 1st capturing group
.*+\n # next line
( ?+ . ) # add a character to the 2nd capturing group
)
)*? # repeat as few times as needed
X .*+\n # X on the first line and advance to next line
?+ # if 1st capturing group is defined, use it, consuming exactly the same number of characters as on the first line
X .*+\n # X on the 2nd line and advance to next line
?+ # if 2st capturing group is defined, use it, consuming exactly the same number of characters as on the first line
X # X on the 3rd line此表達式使用具有自引用捕獲組的前瞻來計算X 之前每行的字元數。它嘗試透過匹配前瞻中指定的條件來匹配垂直格式中的三個 X 字元。
線上示範： https://regex101 .com/r/Xb5l/2
雖然它不能在像Perl 和PCRE 這樣的有限後向的正則表達式風格中直接解決，但可以透過操作匹配的字串來間接確定計數。
以下解決方案透過匹配和計算匹配中出現三個 X 的部分中的字元數來修改 m.buettner 的「部分 PCRE 解決方案」。
^
(?:
(?: # match .+? characters
.
(?= # counting the same number on the following two lines
.*+\n
( ?+ . )
.*+\n
( ?+ . )
)
)+?
(?<= X ) # till the above consumes an X
(?= # that matches the following conditions
.*+\n
?+
(?<= X )
.*+\n
?+
(?<= X )
)
(?= # count the number of matches
.*+\n
( ?+ . ) # the number of matches = length of
)
)* # repeat as long as there are matches on this line
.*\n? # remove the rest of the line此表達式與前一個表達式匹配相同的格式，但它添加了第三個捕獲組併計算該組中匹配字符的長度。透過僅用第三個捕獲組的內容替換匹配項，產生的字串長度表示三 X 形式的數量。
Perl 中的範例用法：
$in =~ s/regex//gmx; $count = length $in;
線上示範： https://regex101.com/r/iqxY1a/1
測試案例：
Test #0: -------------------- X X X result: 1 (X) Test #1: -------------------- ..X.... ..X.... ..X.... result: 1 (.) Test #2: -------------------- ..X.X.. ..X.X.. ....X.. result: 1 (.) Test #3: -------------------- ..X.... ..X.... ...X... result: 0 () Test #4: -------------------- ..X.... ...X... ..X.... result: 0 () Test #5: -------------------- ....X.. .X..X.. .X..... result: 0 () Test #6: -------------------- .X..X.. .X.X... .X.X... result: 1 (.) Test #7: -------------------- .X..X.. .X..X.. .X..X.. result: 2 (.X) Test #8: -------------------- XXX XXX XXX result: 3 (XXX) Test #9: -------------------- X.X.X XXXXX XXXXX .X.X. result: 5 (XXXXX) Test #10: -------------------- 1....X....... 2..X..X...X.... 3X.X...X..X..... 4X....XXXXXX..... 5X..XXX........... 6.....X.......... 7.........X....X 8..X......X....X.... 9..X......X....X....X... A....X..... B.X..X.. C..... XXX XXX XXX . result: 8 (3458.XXX)
以上是正規表示式能否偵測 ASCII 影像中垂直線結構中的三個 X？的詳細內容。更多資訊請關注PHP中文網其他相關文章！
