C Programming Code Examples
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Program to Implement the KMP Pattern Searching Algorithm
/* Program to Implement the KMP Pattern Searching Algorithm
This C Program performs a pattern searching using KMP Pattern Searching algorithm. Pattern searching is used for finding the existence of a substring in a string. The pattern searching in the following has been made case-insensitive. */
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main()
{
char string[88], matchcase[20], c;
int x = 0, j = 0, index;
/*Scanning string*/
printf("Enter string: ");
do
{
fflush(stdin);
c = getchar();
string[x++] = tolower(c);
} while (c != '\n');
string[x - 1] = '\0';
/*Scanning substring*/
printf("Enter substring: ");
x = 0;
do
{
fflush(stdin);
c = getchar();
matchcase[x++] = tolower(c);
} while (c != '\n');
matchcase[x - 1] = '\0';
for (x = 0; x < strlen(string) - strlen(matchcase) + 1; x++)
{
index = x;
if (string[x] == matchcase[j])
{
do
{
x++;
j++;
} while(j != strlen(matchcase) && string[x] == matchcase[j]);
if (j == strlen(matchcase))
{
printf("Match found from position %d to %d.\n", index + 1, x);
return 0;
}
else
{
x = index + 1;
j = 0;
}
}
}
printf("No substring match found in the string.\n");
return 0;
}
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