正则表达式c语言经典实现

正则表达式c语言经典实现

/*
 * test.c
 *
 *  Created on: 2012-12-4
 *      Author: Administrator
 */
#include <stdio.h>
int matchhere(char *,char *);
int matchstar(int c,char *regexp,char *text){
	char *t;
	for(t = text; *t != '\0' &&(*t == c || c=='.');t++);
	do{
		if(matchhere(regexp,t))return 1;
	}while(t-->text);
	return 0;
}
int matchhere(char *regexp, char *text) {
	if (regexp[0] == '\0') {
		return 1;
	}
	if (regexp[1] == '*') {
		return matchstar(regexp[0], regexp + 2, text);
	}
	if (regexp[0] == '$' && regexp[1] == '\0') {
		return *text == '\0';
	}
	if((text[0] != '\0')&&(regexp[0]=='.'|| regexp[0]==text[0])) {
		return matchhere(regexp+1,text+1);
	}
	return 0;
}
int match(char *regexp, char *text) {
	if (regexp[0] == '^')
		return matchhere(regexp + 1, text);
	do {
		if (matchhere(regexp, text)) {
			return 1;
		}
	} while (*text++ != '\0');
	return 0;
}
int main(){
	char *regexp = ".*$";
	char *text = "123";
	if(match(regexp,text)){
		puts("ok");
	}
	return 0;
}