Arrays and Indices

Question

For my next to last for loop, I'm trying to get the odd indices to print 1 and even indices to print 0. I'm having trouble trying to print the even indices.

#include<iostream>
#include <cstdlib>
#include<ctime>

using namespace std;

int main() {
int myArray[10];

//print 0 for ea. element
for (int a = 0; a < 10; a++) {
myArray[a] = 0;
cout << "Element" << a << "= " << myArray[a] << endl;
}

//print random # for ea. element
srand(time(0));
for (int a = 0; a < 10; a++) {
myArray[a] = rand() % 10 + 1;
cout << "Random" << a << "= " << myArray[a] << endl;
}

//print odd # for ea. element
for (int a = 0; a < 10; a++) {
myArray[a] = 2 * a + 1;
cout << "Term" << a << "= " << myArray[a] << endl;
}

//print odd elements=1 and even elements=0
for (int a = 0; a < 10; a++) {
int evenArr = 0;
int oddArr = 1;
myArray[a] = a++;
if (myArray[a] % 2 == 0)
cout << "Even" << a << "= " << evenArr << endl;
else
cout << "Odd" << a << "= " << oddArr << endl;
}

//print elements to multiples of 10 then print backwards
for (int a = 0; a < 10; a++) {
myArray[a] = 10 + 10 * a;
}
for (int a = 9; a >= 0; a--) {
cout << "Multiple" << a << "= " << myArray[a] << endl;
}

system("pause");
return(0);
}

Answer 1

The problem is this line:
myArr[a] = a++;
Doings this results in a being incremented twice per iteration, so you effectively leave out half of the elements. You shouldn't increment/decrement the running variable inside a for-loops body to prevent especially this.
You can use a + 1 instead of a++ since a + 1 won't effect the original value of a.
But I don't see why you would want to do it this way, because this way odd indices will print even and the other way round.

Answer 2

Can you elaborate more what's the problem?

Answer 3

Is this what you mean? you can ask again if I misunderstood your intention ...

for (int a = 0; a < 10; a++) {
int evenArr = 0;
int oddArr = 1;
myArray[a] = a+1;
if (myArray[a] % 2)
cout << "Even" << a << "= " << evenArr << endl;
else
cout << "Odd" << a << "= " << oddArr << endl;
}

Answer 4

Krista, actually I agree with Shadow, the snippet I passed there gives output that was *not* supposed to be, (read Shadow's explanation for reason why). Another way to do that, without the twisted 'if' branch, would be to evaluate the element index in the 'if' branch, instead of the element value.

myArray[a] = a + 1;
if (a % 2 == 0) // <= evaluate index

Either way still, the value assignment to elements here should do with;

myArray[a] = a + 1;

instead of;

myArray[a] = a++;

Answer 5

Thanks guys. Shadow thank you for explaining. Ipang's code output what I wanted.