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C program for pattern matching, pattern matching in c

Pattern matching in C: C programming code to check if a given string is present in an another string, for example, the string "programming" is present in the string "C programming". If it is present, then it's location (i.e. at which position it is present) is printed. We create a function match which receives two character arrays and returns the position if matching occurs otherwise returns -1. We are implementing naive string search algorithm in this C program.

C programming code

#include <stdio.h>
#include <string.h>
 
int match(char [], char []);
 
int main() {
  char a[100], b[100];
  int position;
 
  printf("Enter some text\n");
  gets(a);
 
  printf("Enter a string to find\n");
  gets(b);
 
  position = match(a, b);
 
  if(position != -1) {
    printf("Found at location %d\n", position + 1);
  }
  else {
    printf("Not found.\n");
  }
 
  return 0;
}
 
int match(char text[], char pattern[]) {
  int c, d, e, text_length, pattern_length, position = -1;
 
  text_length    = strlen(text);
  pattern_length = strlen(pattern);
 
  if (pattern_length > text_length) {
    return -1;
  }
 
  for (c = 0; c <= text_length - pattern_length; c++) {
    position = e = c;
 
    for (d = 0; d < pattern_length; d++) {
      if (pattern[d] == text[e]) {
        e++;
      }
      else {
        break;
      }
    }
    if (d == pattern_length) {
      return position;
    }
  }
 
  return -1;
}

Download Pattern matching program.

Output of program:
Pattern matching C program

C program for pattern matching using pointers

#include<stdio.h>
 
int match(char*, char*);
 
main()
{
   char a[100], b[100];
   int position;
 
   printf("Enter some text\n");
   gets(a);
 
   printf("Enter a string to find\n");
   gets(b);
 
   position = match(a, b);
 
   if(position!=-1)
      printf("Found at location %d\n", position+1);
   else
      printf("Not found.\n");
 
   return 0;   
}
 
int match(char *a, char *b)
{
   int c;
   int position = 0;
   char *x, *y;
 
   x = a;
   y = b;
 
   while(*a)
   {
      while(*x==*y)
      {
         x++;
         y++;
         if(*x=='\0'||*y=='\0')
            break;         
      }   
      if(*y=='\0')
         break;
 
      a++;
      position++;
      x = a;
      y = b;
   }
   if(*a)
      return position;
   else   
      return -1;   
}