Searching for a pattern in a given string

belongs to collection: String Interview Questions in C, might ask by the interviewer.

YasminRadwan26

Save to bookmark

2022-06-25

254

Sometimes interviewer asks the question to search a pattern in a given string. There are a lot of algorithms to find the pattern, later we will discuss all the algorithms in detail. Here I am using the Naive algorithm (not a smart algorithm) to search a Pattern.

Suppose a given source string is src[0..n-1] and a pattern is pat[0..m-1]. Here to search the pattern for a given string, we need to slide the pattern string (pat) over source string (src) one by one and check for the match. If the match is found, then slides by 1 again to check for subsequent matches.

Example,
Input: src[] = “How are you”
Patteren: pat[] = “are”
Output: Pattern found at index 4

C programming, Interview questions, C programming Interview-questions,

All Answers

YasminRadwan26

2022-06-25

need an explanation for this answer? contact us directly to get an explanation for this answer

#include <stdio.h>
#include <string.h>
//Function to search the pattern
void searchPattern(char *pSrcString, char* pPattern)
{
    int lenSrcString = strlen(pSrcString); //Get length of src string
    int lenPatString = strlen(pPattern); //Get length of pattern string
    int srcIndex = 0;
    /* A loop to slide pat[] one by one on src*/
    for (srcIndex = 0; srcIndex <= lenSrcString - lenPatString; ++srcIndex)
    {
        int patternIndex;
        /* For current index i, check for pattern match */
        for (patternIndex = 0; patternIndex < lenPatString; ++patternIndex)
        {
            if (pSrcString[srcIndex + patternIndex] != pPattern[patternIndex])
                break;
        }
        // if pat[0...M-1] = src[srcIndex, srcIndex+1, ...srcIndex+M-1]
        if (patternIndex == lenPatString)
        {
            printf("Pattern found at index %d \n", srcIndex);
        }
    }
}
int main()
{
    char src[] = "How are you"; //source string
    char pat[] = "are"; //pattern you want to find
    searchPattern( src,pat); //function to search pattern
    return 0;
}

Output: Pattern found at index 4.

need an explanation for this answer? contact us directly to get an explanation for this answer

total answers (1)