Regular Expression in c,

Regular Expression in c,

Using System; using System. collections. generic; using System. linq; using System. text; using System. threading. tasks; namespace Regular Expression {using System. text. regularExpressions; // The namespace class Program {static void Main (string [] args) of the regular expression {/** Regular Expression matching principle: * 1. only focus on whether a string can be matched, not its location, and other unmatched parts. * 2. greedy mode: the regular expression matches as many strings as possible, which means that it matches the last string that can be matched */while (true) {string str = Console. readLine (); # region metacharacter _ placeholder // the function of the method is to determine whether str matches a custom regular expression rule // 1 ..: represents a placeholder character. It can represent any character. One character must be input. It can be a Chinese Console. writeLine (Regex. isMatch (str, "B. g "); // 2. []: represents a single character in a specified range, you can specify the value of the break, you can also specify the continuous range: 0-9 A-Z a-z valid characters: 0-9 A-Z a-z _ Console. writeLine (Regex. isMatch (str, "B [0-9] g"); // in the regular expression, ^ can only be written at the beginning. If it is written in the middle, ^ is a common character of the Console. W RiteLine (Regex. isMatch (str, "B [0-9A-Z ^ a-z _] g"); Console. writeLine (Regex. isMatch (str, "B [^ 0-9A-Za-z _ ^] g"); // here [0-z] will contain all characters between 0 and Z, it also contains some special symbols // the order in which the range of "B [9-1] g"-[x-y] is being analyzed is reversed. The Console can only be small to large in the order of ASCII codes. writeLine (Regex. isMatch (str, "B [9-1] g"); Console. writeLine (Regex. isMatch (str, "B [0-] g"); // 11-19 Console. writeLine (Regex. isMatch (str, "[11-19]"); // 1 1-1 9 Console. writeLine (Regex. isMatch (str, "B [^ 0-9] g"); // |: or Console. writeLine (Regex. isMatch (str, "[0-9] [0-9] | [0-9] [0-9] [0-9]"); // hjasdgf1234fjhadsjfhas // If strict bid matching is involved, you need to add start ^ and end $: indicates that the character must strictly match the regular Console from start to end. WriteLine (Regex. isMatch (str, "^ [0-9] [0-9] $ | ^ [0-9] [0-9] [0-9] $ ")); // All characters contained in [] are normal characters, not metacharacters. Except ^-requires content to be followed. If matching is required, you can consider using escape \ Console. writeLine (Regex. isMatch (str, @ "^ \ ^ $"); Console. writeLine (Regex. isMatch (str, "^ \ ^ $"); # endregion # region metacharacters _ modifier // *: it is not a placeholder character, it does not represent a single character. It is used to modify * when the first subexpression appears 0 or multiple times: the subexpression is the character before * by default, if you need to represent multiple, use () to include the Console. writeLine (Regex. isMatch (str, "AB * g"); Console. writeLine (Reg Ex. isMatch (str, "^ (AB) * g $"); // +: it is not a placeholder, meaning it does not represent a character, it is used to modify the subexpression that appears once or multiple times before +: the subexpression refers to the character before + by default. To represent multiple, use () contains Console. writeLine (Regex. isMatch (str, "a + g "));//?: It is not a placeholder character, indicating that it does not represent a character, it is used to modify? The previous subexpression appears 0 or 1 time: What is the default value of the subexpression? The character above, if it needs to represent multiple, uses () to include Console. WriteLine (Regex. IsMatch (str, "^? G $ "); // {n, m }:{ n, m} It is not a placeholder character, meaning it does not represent a character, it is used to modify {n, m} the subexpression in front of the Console appears at least n times and at most m times. writeLine (Regex. isMatch (str, "^ [0-9] {3, 4} $"); // {n}: it is not a placeholder, meaning it does not represent a character, it is used to modify the subexpression before {n} and can only appear n times on the Console. writeLine (Regex. isMatch (str, "^ [1-9] [0-9] {17} $ | ^ [0-9] {15} $ | ^ [0-9] {17} [xX] $ ")); // {n ,}: it is not a placeholder character, indicating that it does not represent a character. It is used to modify the subexpression before {n ,} to appear at least n times, the Console is not limited at most. writeLine (Regex. isMatch (str, "^ [0-9] {3 ,}$"); Console. write Line (Regex. isMatch (str, "^ q * $"); # endregion // check whether the logon name contains a special symbol in c #: [^ 0-9A-Za-z _]: it cannot contain Chinese # region short expression // \ d: represents a number, equivalent to [0-9] Console. writeLine (Regex. isMatch (str, @ "^ \ d {3 ,}$"); // \ D: Non-digital Console. writeLine (Regex. isMatch (str, @ "\ D"); // \ s: Empty character: space, tab, line feed Console. writeLine (Regex. isMatch (str, @ "\ s"); // \ S: Non-blank character Console. writeLine (Regex. isMatch (str, @ "\ S"); // \ w: [0-9 a-z A-Z _ Chinese] Console. writeLine (Rege X. isMatch (str, @ "\ w"); // \ W: special symbol Console except for [0-9 a-z A-Z _ Chinese. writeLine (Regex. isMatch (str, @ "\ W"); # endregion} // checks whether the string is a correct domestic phone number, regardless of the extension. // 010-8888888, 010-88888880, or 010 xxxxxxx // 0335-8888888 or 0335-88888888 (area code-phone number) // 10086, 10010, 95595, 95599, 95588 (5 digits) // 13888888888 (11 digits) while (true) {string str = Console. readLine (); // do not try to match the Console one by one. writeLine (Regex. isMatch (str, @ "^ \ d {3, 4} [-]? \ D {7, 8 }$ | ^ [1-9] \ d {4 }$ | ^ 1 [3-9] \ d {9} $ "));} // verify the validity of the email address entered by the user wuhu0723@126.com while (true) {string str = Console. readLine (); // do not try to match the Console one by one. writeLine (Regex. isMatch (str, @ "^ [0-9A-Za-z _] + [@] [0-9A-Za-z _] + [.] [A-Za-z] {2, 5} $ "));}}}}