C++ String Functions with Pointers

[ineedhelpnow]

Assign the first instance of The in movieTitle to movieResult.

Sample program:

#include <iostream>
#include <cstring>
using namespace std;

int main() {
   char movieTitle[100] = "The Lion King";
   char* movieResult = 0;

   <STUDENT CODE>

   cout << "Movie title contains The? ";
   if (movieResult != 0) {
      cout << "Yes." << endl;
   }
   else {
      cout << "No." << endl;
   }

   return 0;
}

I have no idea how to do this. I was thinking to use either the strrchr function or strchr but I'm not sure which one. Something like movieResult=strrchr(movieTitle, ?) but I'm really confused.

 

[johng1]

Here you are working with C strings, not C++ string objects.
As in one of your previous questions, movieTitle (an array) is a pointer to char.
For example, *movieTitle=='T' and *(movieTitle+2)=='e'.
Since movieResult is a pointer to char, the only possible value of movieResult is a pointer.
So look up the function strstr. You'll find the types of the expected parameters and the return value type.
BTW, even with pointer to char, I think it is better to use NULL instead of 0; this reinforces the idea that you're dealing with pointers.

 

[ineedhelpnow]

This is the definition I have of strstr "strstr(str1, str2) Returns char* pointing to first occurrence of string str2 within string str1. Returns 0 if not found. "

How do I use it though?

 

[johng1]

If you want to call (use) a function, you must know exactly the function declaration so you can supply correct arguments. The prototype for strstr (actually there are 2 strstr's in C++; they differ only in const modifiers) is:

const strstr(char* str1,const char* str2);

For a parameter, the modifier const merely is a promise to the compiler that the parameter will not be changed by the function. For example, the compiler will disallow a statement like *str2='a' within the function body of strstr. So now to use strstr, you must supply 2 pointers to char as the arguments. For example strstr(movieResult,NULL) is a valid function call; it's not what you want, though. The return value of strstr is a pointer (non NULL) to the first occurrence of str2 in str1 or NULL if str2 is not a substring of str1. Now I leave to you the proper function call and what you should do with the return value.
Moral of the story: you must know exactly the function's signature (parameters and types) and return value to use it.

 

[ineedhelpnow]

movieResult=strstr(movieTitle, "The");