Example: Substring Replacement (Same Length) in C

// Substring Replacement (Same Length)
#include <stdio.h>
#include <string.h> // For strlen, strstr, strncpy

// Function to replace the first occurrence of a substring
// Assumes replace_with has the same length as find_str
void replace_same_length(char *text, const char *find_str, const char *replace_with) {
    char *match = strstr(text, find_str); // Step 1: Find the first occurrence of find_str

    if (match != NULL) { // Step 2: If found
        // Step 3: Copy replace_with into the location where find_str was found
        // Use strncpy to prevent buffer overflow if lengths mismatch (though assumed same here)
        strncpy(match, replace_with, strlen(replace_with));
    }
}

int main() {
    char buffer[100] = "Hello world, hello C!";
    const char *find = "hello";
    const char *replace = "greet"; // "greetings" is longer, "greet" is same length as "hello"

    printf("Original string: %s\n", buffer);

    replace_same_length(buffer, find, replace); // Step 1: Call the replacement function

    printf("String after replacement: %s\n", buffer);

    // Another example
    char sentence[100] = "The quick brown fox jumps over the lazy dog.";
    replace_same_length(sentence, "fox", "cat");
    printf("Sentence after 'fox' -> 'cat': %s\n", sentence);

    return 0;
}