#include <iostream>
using namespace std;


// CONSTANTS
const int MAX_SIZE = 256;


int get_size(char text[MAX_SIZE])
{
  for (int i=0;i<MAX_SIZE;i++)
  {
    if (!(text[i]))
      return i;
  }
  return MAX_SIZE;
}

int locate(char text[MAX_SIZE], char from[MAX_SIZE], 
           int size_f)
{
  int i2 = 0;
  
  for (int i1 = 0;i1 < MAX_SIZE;i1++)
  {
    if (text[i1] == from[i2])
    {
      i2 ++;
      if (i2 == size_f)
        return i1 - size_f + 1;
    }
    else if (!(text[i1]))
      return -1;
    else
      i2 = 0;
  } 
  
  return -1;
}

char* replace(char text[MAX_SIZE], char to[MAX_SIZE], 
              int where, int size_f, int size_t)
{
  char new_text[MAX_SIZE];
  
  int offs1 = size_f+where;
  int offs2 = size_t+where;
  
  // append text before change
  for (int i1=0; i1 <= where; i1++)
    new_text[i1] = text[i1];      

  // append change
  for (int i2=0; i2 <= size_t; i2++)
    new_text[i2+where] = to[i2];
  
  // append text after change
  for (int i3=0; i3 <= get_size(text)-size_f-where; i3++)
    new_text[i3+offs2] = text[i3+offs1];
  
  return new_text;
}

int main()
{
  char text[MAX_SIZE] = "This is some text, yaddi yaddi.";
  char from[MAX_SIZE] = "some";
  char to[MAX_SIZE]   = "no";
  
  int size_f = get_size(from);
  int size_t = get_size(to);
  
  int where = locate(text, from, size_f);
  
  if (where == -1)
    cout << "Value was not found anywhere inside the text";
  else  
    cout << replace(text, to, where, size_f, size_t);
    
  cin.sync();
  cin.get();
  return 0;   
}