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Basic
Switch Case
Goto
Operators
if Statement
Nested if
While Loop
For Loop
Patterns
Array
2D Array
String Function Example
Pointers
Recursion Function
Structure
Excersises
Others



C Program to Check if the Substring is Present in the Given String


Write a C program to check if the substring is present in the given string.

  • Reads the main string and substring character-by-character until a newline (\n) is encountered.
  • Loops through each character of the main string to check for a potential substring match starting at that index.
  • Compares characters of the substring with the corresponding characters in the main string using nested while.
  • If the entire substring matches, sets a found flag and breaks; prints the result based on this flag.
Example : pgm.c 
#include <stdio.h>

int main() {
    char str[100], substr[50];
    int i = 0, j = 0, found = 0;

    printf("Enter the main string: ");
    while ((str[i] = getchar()) != '\n') {
        i++;
    }
    str[i] = '\0';

    printf("Enter the substring: ");
    while ((substr[j] = getchar()) != '\n') {
        j++;
    }
    substr[j] = '\0';

    // Check for substring match
    for (i = 0; str[i] != '\0'; i++) {
        int k = i, l = 0;

        while (str[k] == substr[l] && substr[l] != '\0') {
            k++;
            l++;
        }

        if (substr[l] == '\0') {
            found = 1;
            break;
        }
    }

    if (found){
        printf("Substring found in the main string.\n");
    }else{
        printf("Substring not found in the main string.\n");
    }

    return 0;
}

Output :

Enter the main string: Welcome Ram
Enter the substring: Ram
Substring found in the main string.