Question

Download the file patternMatch.c from the course website. This file contains part of a program to do pattern matching. The function main looks like this: int main() { char text (40), pattern (40), *position; int textlength, patternlength; printf ("Enter text: "); textlength = readline (text, 40); printf ("Enter pattern: "); patternlength = readline (pattern, 40); position = findmatch (pattern, text, patternlength, textlength); printmessage (position, text, patternlength, textlength); The function readline should read a line of characters from the keyboard. The second argument to the function is the maximum number of characters to read. If a line has more characters than that, the function should ignore the rest of the characters on the line. The function returns the number of characters read. Note that the array should not contain the "in' from the end of the line, nor should it include a terminator character such as "O'. (In other words, for now forget about how C implements strings. The text and pattern arrays are NOT strings.) The program calls readline twice. The first line its reads is called the text, and the second line is called the pattern. The program calls the function findmarch to determine if the pattern matches some portion of the text. If it does, then the function returns a pointer to the location in the text where the match begins. If it does not, then the function returns the pointer NULL. Finally, the program calls the function printmessage to print a message about what happened. If a mateh was not found, then a "no match" message is printed. If a match is found, then the function prints the position in the text where the match begins, and prints the remaining text chars that appear after the match ends. See the example below for details Your job is to write these three functions. You must write them exactly as described for example. Tudmarch must return a pointer to a char. You are also welcome to write other Twitions volu desm appr(opriate, u ԿԻ:45 ՍԼՈՎ ՈՒՏՈՐ ՀԱջ 10 JINN ԱԱԱԱԾ - e rtsit painters and pointunarthen B When pressing a pattern. We should tal the chiamata matches any text chatelet. Se for example the pattern sbaal but not liabh rhhh wild card symbol, which the text abed and s

Answer 1

C code is given below:

#include<stdio.h>
// read line function
int readline(char str[],int maxchar) {
   char ch;
   int ind = 0; // for calculating the length
   scanf("%c",&ch);
   while(ind<40 && ch!='\n') { // this will read the characters until a newline is entered
       str[ind] = ch;
       scanf("%c",&ch);
       ind++;
   }
   return ind; // the ind will be the length of the string
}
// for finding the match
char* findmatch(char pattern[], char text[],int patternlength, int textlength) {
   for(int i=0;i<=(textlength-patternlength);i++) { // we go to the last possible index of match which is (textlength-patternlength)
       if((pattern[0] == '?')||(text[i] == pattern[0])) { // if the fist char of pattern match or it is a wildcard then there can be a match
           int j = 0, k = i;
           for(;(j<patternlength) && (k<textlength);j++,k++) {// now we match character by character
               if(pattern[j] == '?') // if there is a wildcard in pattern, it's okay
                   continue;
               else if(pattern[j] != text[k]) { // otherwise if it does not match then no match
                   break;
               }
           }
           if(j == patternlength) // if we traversed whole pattern it means it did not break, which means there is a match at index i.
               return &text[i]; // so return address of match
       }
   }
   return NULL; // otherwise return null
}
void printmessage(char *position, char text[],int patternlength, int textlength) {
   if(position == NULL)
       printf("no match\n");
   else {
       int ind = (position - text); // index will be the difference of base address and address of match
       printf("The pattern was found at char %d. ",ind + 1);
       printf("The remaining text chars are: ");
       ind += (patternlength); // go to the end of match
       while(ind<textlength) {
           printf("%c",text[ind]); // printing the chars after match
           ind++;
       }
       printf("\n");
   }
}
int main() {
   char text[40], pattern[40], *position;
   int textlength, patternlength;

   printf("Enter text: ");
   textlength = readline(text, 40);
   printf("Enter Pattern: ");
   patternlength = readline(pattern, 40);
   position = findmatch(pattern, text, patternlength, textlength);
   printmessage(position, text, patternlength, textlength);
}

Sample input and output:

chandan@chandan-Vostro-15-3568:~$ ./a.out Enter text: abcdefghi Enter Pattern: ?def? The pattern was found at char 3. The remaining text chars are: hi chandan@chandan-Vostro-15-3568:~$ ./a.out Enter text: abcdefghi Enter Pattern: b?c no match chandan@chandan-Vostro-15-3568:~$ ./a.out Enter text: abcdefghi Enter Pattern: b??ef The pattern was found at char 2. The remaining text chars are: ghi

Screenshot of the code is given below:

#include<stdio.h> int readline(char str[], int maxchar) { char ch; int ind = 0; scanf("%c",&ch); while(ind<40 && ch!='\n') { str[ind] = ch; scanf("%c",&ch); ind++; return ind; char* findmatch(char pattern[], char text[], int patternlength, int textlength) { for(int i=0;i<=(textlength-patternlength); i++) { if((pattern[0] == '?') || (text[i] == pattern[o])) { int j = 0, k = i; for(;(j<patternlength) && (k<textlength); j++, K++) { if(pattern[j] == '?') continue; else if(pattern[j] != text[k]) { break; if(j == patternlength) return &text[i]; 27 29 30 return NULL; } void printmessage(char *position, char text[], int patternlength, int textlength) { if(position == NULL) printf("no match\n"). 31 32

", ind + 1); I PUSILIUIL -= NULL) printf("no match\n"); else { int ind = (position - text); printf("The pattern was found at char %d printf("The remaining text chars are: "); ind += (patternlength); while(ind<textlength) { printf("%c", text[ind]); ind++; printf("\n"); int main() { char text(40), pattern [40], *position; int textlength, patternlength; printf("Enter text: "); textlength = readline(text, 40); printf("Enter Pattern: "); patternlength = readline (pattern, 40); position = findmatch(pattern, text, patternlength, textlength); printmessage(position, text, patternlength, textlength);

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