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  1. #include <stdio.h>
  2. #include <string.h>
  3. #include <stdlib.h>
  4.  
  5. char* replaceSubstring(const char* str, const char* oldSub, const char* newSub) {
  6.     const char* pos = strstr(str, oldSub);
  7.     if (!pos) return strdup(str); // oldSub not found, return original string
  8.  
  9.     size_t beforeLen = pos - str;
  10.     size_t oldLen = strlen(oldSub);
  11.     size_t newLen = strlen(newSub);
  12.     size_t afterLen = strlen(pos + oldLen);
  13.  
  14.     // Allocate memory for new string
  15.     char* result = malloc(beforeLen + newLen + afterLen + 1);
  16.     if (!result) return NULL;
  17.  
  18.     // Copy parts
  19.     memcpy(result, str, beforeLen);
  20.     memcpy(result + beforeLen, newSub, newLen);
  21.     memcpy(result + beforeLen + newLen, pos + oldLen, afterLen);
  22.     result[beforeLen + newLen + afterLen] = '\0';
  23.  
  24.     return result;
  25. }
  26.  
  27. int main() {
  28.     const char* original = "Hello World!";
  29.     const char* oldSub = "World";
  30.     const char* newSub = "C";
  31.  
  32.     char* replaced = replaceSubstring(original, oldSub, newSub);
  33.     printf("Result: %s\n", replaced);
  34.  
  35.     free(replaced);
  36.     return 0;
  37. }
  38.  
  39.  
Success #stdin #stdout 0s 5320KB
comments (?)
stdin 
Standard input is empty
stdout 
Result: Hello C!
https://ideone.com/VO5cCg
language:
C (gcc 8.3)
created:
8 days ago
visibility:
public

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