Looping vector in C++ causes invalid iterations [closed] - c++

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I have written a small program that takes inputs as string which is stored in a vector.
Looping through the vector causes many empty strings being printed before actual output.
I have copied the sample lines below.
int main(){
int totalStrings;
string inputs;
vector<string> testCases(totalStrings);
cin>>totalStrings;
while(cin>>inputs)
testCases.push_back(inputs);
for(vector<string>::iterator it=testCases.begin();it!=testCases.end();++it)
printCustom(*it);
return 0;
}
I tried printing the size of the string in the printCustom function. I had hundreds of zero printed before the actual input

Answer 1

vector<string> testCases(totalStrings);
This line of code has two issues:
totalStrings is uninitialized and thus garbage,
vector(N) creates a vector of size N default-initialized elements, as though you had called resize rather than reserve on the vector.
What you wanted was:
std::cin >> totalStrings;
std::vector<std::string> testCases;
testCases.reserve(totalStrings);

Answer 2

Try the following:
cin>>totalStrings;
vector<string> testCases(totalStrings);
You have initialized totalStrings (as int) without a proper value, and you have used it to initialize the vector. This is bad times!!
Moreover, please check your indentations (a very good practice).
All the best.
To explain further (Please check the code, if required):
In your code, you wrote:
int totalStrings;
string inputs;
vector<string> testCases(totalStrings);
Point 1:
In the first line, you have not initialized totalStrings to anything. In such case depending on the computer, the vector can be initialized to any possible length. In my computer, if I do the following:
int totalStrings;
cout << totalStrings; // printing un-initialized totalStrings
string inputs;
vector<string> testCases(totalStrings);
The code prints zero, meaning totalStrings is, by magic, initialized to zero. But it may or may not be the case with your system.
Point 2:
Now when you initialize a vector with a predefined size you have provided space for values but there is no value, by default. And since you are using push_back method, you are enlarging the vector and adding to the end of the vector.
Implication of point 1 and point 2 in your final output;
Therefore, when you print (using the for loop and iterator) you will get as many zeros as the initial length (defined by totalStrings and the vector initialization); and after printing the initial vector it will print the strings that you have entered manually.
Please play with the following code to get a feeling. I hope this helps.
#include <string>
#include <vector>
#include <iostream>
using namespace std;
int main() {
int totalStrings;
cout << "Please enter initial vector length: ";
cin >> totalStrings;
vector<string > testCases(totalStrings);
string inputs;
cout << "Enter the strings into the vector [Enter -1 to finish]: ";
while(true) {
cin >> inputs;
if (inputs == "-1") { break; }
testCases.push_back(inputs);
cout << "Next? ";
}
for (vector<string>::iterator it = testCases.begin(); it != testCases.end(); ++it)
cout << ' ' << it->size();
return 0;
}