I am trying to take sentence as an input from the user in the below code. eg. Input -

9

do or die

#include<iostream>
using namespace std;

int main(){
    int n;
    cout<<"Enter the length of the sentence: ";
    cin>>n;
    cin.ignore();
    char array[n 1]; 
    cin.getline(array,n);
    cin.ignore();
    cout<<array[7]<<endl;
    cout<<array[8]<<endl;

While printing the array[7], I am getting 'i' as my output, but while printing array[8] I am expecting 'e' as my output but I did not get anything as an output. I have declared character array of size (n 1), which means array[n] should be null character but why array[8] is coming out to be null character?

Am I doing wrong somewhere?

CodePudding user response：

std::istream::getline(char* s, streamsize n):

1. Extracts characters from the stream as unformatted input and stores them into s as a c-string.
2. n is the maximum number of characters to write to s, including the terminating null character.

If you want to read your 9 characters of the sentence, not only your buffer needs to be 10 characters long, but also n in getline needs to be 10.

https://www.cplusplus.com/reference/istream/istream/getline/

CodePudding user response：

The answer to the actual problem is addressed by @SKCoder, so I just want to add that input handling works better with std::string and I changed the code accordingly:

#include <iostream>

int main(){
    size_t n;
    std::cout<<"Enter the length of the sentence: ";
    std::cin>>n;
    std::cin.ignore();
    std::string str;
    std::getline(std::cin, str);
    std::cin.ignore();
    std::cout<<str.substr(str.length()-2, 2)<<"\n";
    std::cout << (str.length() != n? "length is wrong": "length is correct") << "\n";
}

I usually don't use using namespace std; to avoid namespace clashes, but in this case it may make sense. Using a string, you don't need the length anymore, so you can use it to test valid input.