Regular expression pattern match in a string, I only checked with * as wild card, other wild card characters are easy implement but I havent done that.
any problems you can email me @ rramaswa@usc.edu
platform - Unix/Linux, havent tested in windows, should'nt be a problem unless some standard header files are missing.
#include <stdio.h> #include <stdlib.h> #include <string.h> int index; int main() { char *reg_str,*str; int flag = 0; int reg_index = 0; int i = 0; int reg_len = 0; int *arr; int arr_count = 0; int reg_flag = 0; int Find_Match(char c,int flag, char *str,int *arr, int *arr_count); reg_str = (char *)malloc(100); str = (char *)malloc(100); arr = (int *)malloc(100 *sizeof(int)); index = 0; printf("Enter the regular expression ..\n"); gets(reg_str); printf("\nEnter the string ..\n"); gets(str); reg_len = strlen(reg_str); for(i = 0;i < reg_len;i++) { if(reg_str[i] == '*') { //reg_index++; flag = 1; free(arr); arr_count = 0; } else { if(Find_Match(reg_str[i],flag,str,arr,&arr_count) == 0) { printf("pattern not found ...\n"); reg_flag = 1; break; } } } if(reg_flag == 0) printf("reg exp pattern found in the string ..\n"); return 0; } int Find_Match(char c,int flag, char *str,int *arr, int *arr_count) { int i = 0; int counter = 0; int arr_index = 0; if(flag == 0) { if(str[index] == c) { index++; return 1; } else { return 0; } } else { if(*arr_count == 0) { for(i = index;str[i] != '\0';i++) { if(str[i] == c) { arr[*arr_count] = i; *arr_count = *arr_count + 1; if(counter == 0) { index++; counter++; } } } } else { for(i = 0;i < *arr_count;i++) { if(arr[i] == -1) continue; arr_index = arr[i] + 1; if(str[arr_index] == c) { arr[i] = arr_index; if(counter == 0) { index = arr_index + 1; counter++; } } else { arr[i] = -1; } } } } if(counter == 0) return 0; else return 1; }
Dont use "gets( )" for accepting string input from user -- It is a bad programming practice and the function itself is flawed as it doesnt check for buffer overflows. Use [search]fgets( )[/search] instead.
Avoid use of globals if possible -- there is no condition where the program cant be done without using globals. Using globals prevents your algo or program being used as a part of a larger program.
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