Q:

C program for pattern matching

hamza
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2022-05-18
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C program for pattern matching

Pattern matching in C: C program to check if a string is present in an another string, for example, the string "programming" is present in the string "C programming". If it's present, then its location (i.e. at which position it's 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 program.

C programming,
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hamza
2022-05-18
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#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;
}

Output of program:

Enter sume text:

computer programming is fun

Enter a string to find

programming is fun

Found at location 10

 

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