Switch statement (string) keeps selecting default value unless its zero - c++

Question

Switch statement only works when I change the value between the brackets to 0 in cout << getDayOfWeek(0);.
Any number between 1-6 selects the default value "Invalid Day Number".
There isn't any issues (no issues found).
I tried retyping it from scratch and nothing worked.
The code is supposed to print out the day when I enter its number, but it only works with 0. If I put other numbers, it selects the default value.
#include <iostream>
#include <cmath>
#include <string>
#include <cstring>
using namespace std;
string getDayOfWeek(int dayNum) {
string dayName;
switch (dayNum) {
case 0:
dayName = "Sunday";
break;
switch (dayNum)
case 1:
dayName = "Monday";
break;
switch (dayNum)
case 2:
dayName = "Tuesday";
break;
switch (dayNum)
case 3:
dayName = "Wednesday";
break;
switch (dayNum)
case 4:
dayName = "Thursday";
break;
switch (dayNum)
case 5:
dayName = "Friday";
break;
switch (dayNum)
case 6:
dayName = "Saturday";
break;
default:
dayName = "Invalid Day Number";
}
return dayName;
}
int main()
{
cout << getDayOfWeek(5);
return 0;
}

Answer 1

You're using the switch statement incorrectly. The code should look like this:
switch(dayNum){
case 0:
// do something
break;
case 1:
// do something
break;
case 2:
// do something
break;
case 3:
// do something
break;
case 4:
// do something
break;
case 5:
// do something
break;
case 6:
// do something
break;
default:
// do something
break;
}
You shouldn't repeat the switch statement over and over again; just keep the first one.

Answer 2

You won't need switch (dayNum) inside the switch statement.
They will create nested switch statements and leave only case 0 and default in the first switch statement.
Try this:
#include <iostream>
#include <cmath>
#include <string>
#include <cstring>
using namespace std;
string getDayOfWeek(int dayNum) {
string dayName;
switch (dayNum) {
case 0:
dayName = "Sunday";
break;
case 1:
dayName = "Monday";
break;
case 2:
dayName = "Tuesday";
break;
case 3:
dayName = "Wednesday";
break;
case 4:
dayName = "Thursday";
break;
case 5:
dayName = "Friday";
break;
case 6:
dayName = "Saturday";
break;
default:
dayName = "Invalid Day Number";
}
return dayName;
}
int main()
{
cout << getDayOfWeek(5);
return 0;
}

Answer 3

You could avoid the switch statement by using an array:
static const char day_names[] =
{
"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"
};
const std::string day_of_week = day_names[dayNum];
The switch statement adds more lines of code to your project, which increases complexity and the probability of defects.