C Program for Naive algorithm for Pattern Searching

Given a text txt[0..n-1] and a pattern pat[0..m-1], write a function search(char pat[], char txt[]) that prints all occurrences of pat[] in txt[]. You may assume that n > m.

Examples:

Input:  txt[] = "THIS IS A TEST TEXT"
        pat[] = "TEST"
Output: Pattern found at index 10

Input:  txt[] =  "AABAACAADAABAABA"
        pat[] =  "AABA"
Output: Pattern found at index 0
        Pattern found at index 9
        Pattern found at index 12
pattern-searching

Pattern searching is an important problem in computer science. When we do search for a string in notepad/word file or browser or database, pattern searching algorithms are used to show the search results.

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C

filter_none

edit
close

play_arrow

link
brightness_4
code

// C program for Naive Pattern Searching algorithm
#include <stdio.h>
#include <string.h>
  
void search(char* pat, char* txt)
{
    int M = strlen(pat);
    int N = strlen(txt);
  
    /* A loop to slide pat[] one by one */
    for (int i = 0; i <= N - M; i++) {
        int j;
  
        /* For current index i, check for pattern match */
        for (j = 0; j < M; j++)
            if (txt[i + j] != pat[j])
                break;
  
        if (j == M) // if pat[0...M-1] = txt[i, i+1, ...i+M-1]
            printf("Pattern found at index %d \n", i);
    }
}
  
/* Driver program to test above function */
int main()
{
    char txt[] = "AABAACAADAABAAABAA";
    char pat[] = "AABA";
    search(pat, txt);
    return 0;
}

chevron_right


Output:

Pattern found at index 0 
Pattern found at index 9 
Pattern found at index 13

Please refer complete article on Naive algorithm for Pattern Searching for more details!



My Personal Notes arrow_drop_up


Article Tags :

Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.