String Find Does Not Find Substring As Expected - c++

Question

I am creating a code that lets the user choose what they'd like to perform from a menu. When I run my code I select choice 'E' and I enter the word I want to be searched. The result comes out that the word is not in the sentence even though it is. Any reason why ? Thank you in advance
#include <iostream>
#include <cmath>
#include <cstdlib>
#include <string>
#include <algorithm>
#include <cctype>
using namespace std;
int main()
{
string s;
char selection;
string w;
cout << "Enter a paragraph or a sentence : " ;
getline(cin, s);
int sizeOfString = s.length();
//cout << "The paragraph has " << sizeOfString << " characters. " << endl; ***Dummy call to see if size works.
//cout << "You entered " << s << endl; *** Dummy function !!
cout << "" << endl;
cout << " Menu " << endl;
cout <<" ------------------------" << endl;
cout << "" << endl;
cout << "A -- Convert paragraph to all caps " << endl;
cout << "B -- Convert paragraph to all lowercase " << endl;
cout << "C -- Delete whitespaces " << endl;
cout << "D -- Split words & remove duplicates " << endl;
cout << "E -- Search a certain word " << endl;
cout << "" << endl;
cout << "Please select one of the above: " ;
cin >> selection;
cout << "" << endl;
switch (selection) //Switch statement
{
case 'a':
case 'A': cout << "You chose to convert the paragraph to all uppercase" << endl;
cout << "" << endl;
for(int i=0; s[i]!='\0'; i++)
{
s[i]=toupper(s[i]);
}
cout << "This is it: " << s << endl;
break;
case 'b':
case 'B': cout << "You chose to convert the paragragh to all lowercase" << endl;
cout << "" << endl;
for (int i=0; s[i] !='\0'; i++)
{
s[i]=tolower(s[i]);
}
cout << "This is it: " << s << endl;
break;
case 'c':
case 'C': cout << "You chose to delete the whitespaces in the paragraph" << endl;
cout << "" << endl;
for(int i=0; i<s.length(); i++)
if(s[i] == ' ') s.erase(i,1);
cout <<"This is it: " << s << endl;
break;
case 'd':
case 'D': cout << "You chose to split the words & remove the duplicates in the paragraph" << endl;
cout << "" << endl;
/*char arrayOne[] = s;
for (int i=0; i< s.length; i++)
{
cout << arrayOne[i] << endl;
}*/
case 'e':
case 'E': cout << "You chose to search for a certain word in the paragraph. " << endl;
cout << "" << endl;
cout << "Enter the word you want to search for: ";
cin >> w;
s.find(w);
if (s.find(w) == true)
{
cout << w << " was found in the paragraph. " << endl;
}
else if (s.find(w) != true);
{
cout << w << " was not found in the paragraph. " << endl;
}
}
return 0;
}

Answer 1

std::string::find returns the sub-string position, not a boolean. Check the documentation.
if equal to std::string::npos, instance is not found, else, if (greater or equal to zero) it is found.
So:
if ( s.find( w ) )
Should be:
if ( s.find( w ) != std::string::npos )
And, by the way:
s.find(w);
if (s.find(w) == true)
{
cout << w << " was found in the paragraph. " << endl;
}
else if (s.find(w) != true);
{
cout << w << " was not found in the paragraph. " << endl;
}
Should be:
if ( s.find( w ) != std::string::npos )
cout << w << " was found in the paragraph. " << endl;
else // no need to test again!
cout << w << " was not found in the paragraph. " << endl;

Answer 2

Your problem is with
if (s.find(w) == true)
find() returns the position of the found string not true or false. If you want to check if it finds the word use
if (s.find(w) != std::string::npos)

Answer 3

I want to suggest the following to simplify your development / test effort:
bool DEVELOPEMENT_MODE = true;
int t247(void)
{
std::string s;
char selection;
std::string w;
std::cout << "Enter a paragraph or a sentence : " ;
// instead of ONLY run-time fetch of paragraph or sentence
if(DEVELOPEMENT_MODE)
{
// for developement use:
std::stringstream ss;
// TEST STRING
ss << "the quick brown fox jumped over the lazy dog";
s = ss.str(); // fill in test input
size_t sizeOfString = s.length(); // note: not int
// ***Dummy unit test to see if size works.
std::cout << "The paragraph has " << sizeOfString
<< " characters. " << std::endl;
// ***Dummy unit test
std::cout << "You entered " << s
<< std::endl;
}
else
{
// for final test use run time entry of sentence
getline(std::cin, s);
}
//...
As you get each function working, add more complexity to the test string (using the editor you normally use).
I often use argc or argv[1] (of main) to select which test to run.
Update:
By the way, you will find it difficult to read a paragraph using getline() without a loop.
However, the DEVELOPMENT_MODE code (with stringstream) can trivially create a paragraph.
ss << "the quick brown fox jumped over the lazy dog";
can be easily expanded ... c++ auto-magically concatenates lines into a single line:
ss << "the quick brown fox jumped over the lazy dog"
"quick brown fox jumped over the lazy dog the"
"brown fox jumped over the lazy dog the brown";
But the above is not yet a paragraph.
The following is a 3 line paragraph:
ss << "the quick brown fox jumped over the lazy dog\n"
"quick brown fox jumped over the lazy dog the\n"
"brown fox jumped over the lazy dog the brown\n";