Comparing char array in c++ - c++

Question

I need help in c++. I want to compare char array. So, I did some coding. Unfortunately, it always comes out an error. I can't run it. Here I attached the code. Please help me fix this code. I want to check if the conclusion equal to sentence 1 then it is invalid but if it's not equal sentence 1 then it is valid. Help me, please. Thank you.
int number;
char sentence[number];
char rules[50];
char statement[50];
char premis1[100];
char premis2[100];
char conclusion[100];
cout<<"How many sentence you want to insert:";
cin>>number;
cout<<endl;
for(int i=0; i<number; i++)
{
cout<<"Enter sentence ";
cout<<i+1;
cout<<":";
cin>>sentence[i];
cin.ignore();
}
cout<<"Enter premis 1:";
cin.getline(premis1,100);
cin.ignore();
cout<<"Enter premis 2:";
cin.getline(premis2,100);
cin.ignore();
cout<<"Enter conclusion:";
cin.getline(conclusion,100);
cin.ignore();
for(int i=0;i<number;i++)
{
if(strcmp(conclusion,sentence[0],)==0)
{
cout<<"Statement is invalid."<<endl;
cout<<endl;
}
else if(strcmp(conclusion,sentence[0])!=0)
{
cout<<"Statement is valid."<<endl;
}
else
cout<<"exit"<<endl;
}

Answer 1

Your mistakes you've made in the program:
You never initialized number but used in sentence[], still it's invalid even after number's declaration, that's because the compiler must know the exact value of the array length to be defined.
You've defined sentence as a char array but from your code, it seems like you wanted to store a full sentence into each element of array, which is impossible. Use std::string here.
You're doing strcmp() with the first character of char array, not the sentence with conclusion.
Aside: Please don't forget to include the important header files which are common to the code and we must assume your program is incomplete, because it has a lack of main() and statement(s), such as strcmp(...,...',' - incomplete).
Redesigned the program (notice that using namespace std statement is used here because it's just a small program to demonstrate and for sake of simplicity and getting rid of std:: prefixes everywhere):
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main(void) {
int number = 0;
vector<string> sentence;
string tempSentence;
string conclusion;
cout << endl;
cout << "How many sentences you want to insert? ";
cin >> number;
for (int i = 0; i < number; i++) {
fflush(stdin);
cout << "Enter sentence " << (i + 1) << ": ";
getline(cin, tempSentence);
sentence.push_back(tempSentence);
}
cout << "Enter conclusion: ";
getline(cin, conclusion);
if (conclusion == sentence[0])
cout << "The statement is invalid." << endl;
else if (conclusion != sentence[0])
cout << "The statement is valid." << endl;
else
cout << "EXIT" << endl;
return 0;
}
I've taken std::vector<> of std::string here to insert a single string in defined number of sentences given in a dynamic way in each iteration (from #include <vector>) and used std::string rather than char arr[], it's easy to compare strings here.
Sample Output:
$ g++ -o prog prog.cpp; ./prog
How many sentences you want to insert? 3 // --- INPUT
Enter sentence 1: This is the first sentence.
Enter sentence 2: This is the second sentence.
Enter sentence 3: This is the third sentence.
Enter conclusion: This is NOT the first sentence.
The statement is valid. // first sentence != conclusion // --- OUTPUT