Post Increment/Decrement

Part of the Fundamentals section of Coddy's C++ journey — lesson 19 of 74.

In the previous lesson, we covered the increment (++) and decrement (--) operators. These operators have two forms: prefix and postfix.

Knowing which form to use matters in real programs — for example, when tracking a game score, counting loop iterations, or advancing through a list of items.

The prefix form is written before the variable (e.g., ++x or --x), and the postfix form is written after the variable (e.g., x++ or x--).

The difference between the two forms is subtle but important:

Prefix form: Increments/decrements the variable and then returns the new value.
Postfix form: Returns the current value of the variable and then increments/decrements it.

Here's an example to illustrate the difference:

int x = 5;
int y = x++;
// y = 5, x = 6 (postfix)

int a = 5;
int b = ++a;
// b = 6, a = 6 (prefix)

In the first case, y is assigned the original value of x (5), and then x is incremented to 6. In the second case, a is incremented first, and then its new value (6) is assigned to b.

The same logic applies to the decrement operator:

int x = 5;
int y = x--;
// y = 5, x = 4 (postfix)

int a = 5;
int b = --a;
// b = 4, a = 4 (prefix)

Challenge

Beginner

You are given a code with initializations of x, y, and z. (Don't delete these lines!)

Your task is to use the increment/decrement operators to perform the following operations, in this order:

Use the postfix increment operator to assign the current value of x to a and then increment x.
Use the prefix decrement operator to decrement y and assign its new value to b.
Use the postfix decrement operator to assign the current value of z to c and then decrement z.

After performing these operations, print the values of a, b, c, x, y, and z to the console in the following format:

a: [value of a]
b: [value of b]
c: [value of c]
x: [value of x]
y: [value of y]
z: [value of z]

Cheat sheet

Increment (++) and decrement (--) operators have two forms:

Prefix form (++x, --x): Increments/decrements the variable first, then returns the new value
Postfix form (x++, x--): Returns the current value first, then increments/decrements the variable

Examples:

int x = 5;
int y = x++;  // y = 5, x = 6 (postfix)

int a = 5;
int b = ++a;  // b = 6, a = 6 (prefix)

int x = 5;
int y = x--;  // y = 5, x = 4 (postfix)

int a = 5;
int b = --a;  // b = 4, a = 4 (prefix)

Try it yourself

#include <iostream>

int main() {
    int x = 10;
    int y = 20;
    int z = 30;
    
    int a, b, c;
    
    // Type your code below
    
    
    // Don't change the lines below
    std::cout << "a: " << a << std::endl;
    std::cout << "b: " << b << std::endl;
    std::cout << "c: " << c << std::endl;
    std::cout << "x: " << x << std::endl;
    std::cout << "y: " << y << std::endl;
    std::cout << "z: " << z << std::endl;
    
    return 0;
}