Question

I need program to calculate the number of seconds since midnight.
For example, suppose the time is 1:02:05 AM.
Since there are 3600 seconds per hour and 60 seconds per minutes,
it has been 3725 seconds since midnight (3600 * 1 + 2 * 60 + 5 = 3725).
The program asks the user to enter 4 pieces of information: hour, minute, second, and AM/PM.
The program will calculate and display the number of seconds since midnight.
Modify the program by adding error checking loops. Hour must be a number from 1 to 12.
Minute and second must be numbers from 0 to 59. Also check whether “AM” or “PM” is entered.
Every time an invalid value is entered,
display an error message and ask the user to re-enter a valid value immediately.
[Hint: be very careful when the hour is 12].

The following is an example:

Enter hour: 0
Hour must be from 1 to 12.
Enter hour: 13
Hour must be from 1 to 12.
Enter hour: 12
Enter minute: -1
Minute must be from 0 to 59.
Enter minute: 60
Minute must be from 0 to 59.
Enter minute: 14
Enter second: -1
Second must be from 0 to 59.
Enter second: 60
Second must be from 0 to 59.
Enter second: 47
Enter AM or PM: FM
Please enter AM or PM
Enter AM or PM: PM
Seconds since midnight: 44087

Answer 1

#include <iostream>

using namespace std;

int readInt(int min, int max, string msg) {
        int x;
        cout << msg;
        cin >> x;
        while(x < min || x > max) {
                cout << "Value must be from " << min << " to " << max << "." << endl;
                
                cout << msg;
                cin >> x;
        }
        return x;
}

int main() {
        int h, m, s;
        string amPm;

        h = readInt(1, 12, "Enter hour: ");
        m = readInt(0, 59, "Enter minute: ");
        s = readInt(0, 59, "Enter second: ");

        cout << "Enter AM or PM:";
        cin >> amPm;

        while(amPm != "AM" && amPm != "PM") {
                cout << "Please enter AM or PM" << endl;    
                cout << "Enter AM or PM:";
                cin >> amPm;
        }

        long seconds = 0;
        seconds += s;
        seconds += m * 60;

        if(h == 12) {
                h = 0;
        }

        seconds += h * 60 * 60;

        if(amPm == "PM") {
                seconds += 12 * 60 * 60;
        }

        cout << "Seconds since midnight: " << seconds << endl;

}

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