How to do a input validation with a string of array? - c++

Question

I'm writing a program where I have to input a month which follows with an output of how many days are in that month. However, I also have to write a code where if the input is not a valid month, it shows an error message. I haven't been able to figure out how to output that error statement. I already figured out the rest though.
I have tried the while loop, but it has not worked for me. I know I must be doing something wrong, but I don't know how to fix it.
#include <iostream>
#include <string>
using namespace std;
int main()
{
const int MONTHS = 12;
int days[MONTHS] = { 31, 28, 31, 30,
31, 30, 31, 31,
30, 31, 30, 31 };
string m;
string i[MONTHS] = { "January", "February", "March",
"April", "May", "June", "July",
"August", "September", "October",
"November", "December" };
cout << "Enter the name of the month: " << endl;
cin >> m;
while (m < MONTHS)
{
cout << "Invalid month entered! Exit the program to try again."
<< endl;
}
cout << endl;
for (int count = 0; count < MONTHS; count++)
if (m == i[count])
{
cout << "There are " << days[count] << " days in "
<< i[count] << "." << endl;
}
return 0;
}
This is the expected result whenever the user inputs a invalid month.
Input the name of a month: Orion
Orion is not the name of a month.

Answer 1

Your while loop is trying to compare m (a string) with MONTHS (the integer 12). Rather than try to fix that, my suggestion is to adjust the code following your for loop. You're already comparing m to each month in the array, right? If m matches, there's no need to continue looping, so you can simply return at that point. Then, if the for loop completes without a match, you know the month was invalid and can report it. Something like this:
for (int count = 0; count < MONTHS; count++)
if (m == i[count])
{
cout << "There are " << days[count] << " days in "
<< i[count] << "." << endl;
return 0;
}
cout << m " is not the name of a month." << endl;
return 1;

Answer 2

There are a couple of little problems contributing to your error.
The first is that you are comparing string m to int MONTHS. That won't work (possibly at all, but at the very least) the way you expect it.
Second, as others have mentioned, there is nothing inside your loop to end the loop. You will want to reset the value of m that way you don't get an infinite loop.
Here is a suggestion of something you could do that should work as you want it to:
NOTE: it requires an std::map
#include <iostream>
#include <string>
#include <map> // if you wanted to do it this way
using namespace std;
int main()
{
const int MONTHS = 12;
int days[MONTHS] = { 31, 28, 31, 30,
31, 30, 31, 31,
30, 31, 30, 31 };
string m;
map<string, int> i = { ("January", 0}, "February", 1}, "March", 2},
{"April", 3}, {"May", 4}, {"June", 5}, {"July", 6},
{"August, 7}", {"September, 8}", {"October, 9}",
{"November, 10}", {"December, 11}" };
cout << "Enter the name of the month: " << endl;
cin >> m;
while (m.find(m) == m.end())
{
cout << "Invalid month entered! Exit the program to try again."
<< endl;
cout << "Enter the name of the month: " << endl;
cin >> m;
}
cout << endl;
cout << "There are " << days[i[m]] << " days in "
<< m << "." << endl;
return 0;
}

Answer 3

I guess this is an assignment? For the main function you could use a map.
Here are some hints so you can complete the task.
Also remember that string comparison is case sensitive which needs to be addressed.
#include <stdio.h>
#include <string>
#include <map>
struct comparer
{
public:
bool operator()(const std::string x, const std::string y) const
{
return x.compare(y)==0;
}
};
int main()
{
map<string, int> months;
months.insert(pair<string, int>("january", 31));
months.insert(pair<string, int>("february", 28));
months.insert(pair<string, int>("mars", 31));
months.insert(pair<string, int>("april", 30));
cout << "Enter the name of the month: " << endl;
cin >> m;
std::map<std::string, int, comparer>::iterator it=months.find(m);
if(it!=months.end())
printf("The number of days is %d\n",(*it).second);
else
printf("Error, the month not found\n");
}