Increment and decrement operators - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed increment operators

What is the output of the following C code?

C

int main() {
    int a = 5;
    int b = a++ + ++a;
    printf("%d\n", b);
    return 0;
}

A 10

B 11

C 12

D 13

💡 Hint

Remember that a++ uses the value before increment, ++a increments before use.

Initially, a=5. a++ returns 5 then a becomes 6. ++a increments a to 7 then returns 7. So b = 5 + 7 = 12.

❓ Predict Output

intermediate

Value of variable after increments

What is the value of variable x after executing this code?

C

int main() {
    int x = 3;
    x = ++x + x++ + ++x;
    printf("%d\n", x);
    return 0;
}

A 14

B 13

C 12

D 15

💡 Hint

Evaluate each increment carefully and track x's value step by step.

Step 1: ++x increments x to 4 and returns 4. Step 2: x++ returns 4 then increments x to 5. Step 3: ++x increments x to 6 and returns 6. Sum: 4 + 4 + 6 = 14, but x is assigned this sum, so x=14. However, the expression uses x on left and right, so the final x is 14. But the question asks for x after assignment, which is 14.

🔧 Debug

advanced

Identify the error in increment usage

Which option will cause a compilation error in C?

C

int main() {
    int a = 5;
    int b = /* expression */;
    printf("%d\n", b);
    return 0;
}

A b = ++a + a++;

B b = a+++++a;

C b = a++ + ++a;

D b = a++ + a++ + ++a;

💡 Hint

Look carefully at the operator sequences and how C parses them.

Option B has 'a+++++a' which is invalid because C cannot parse '+++++' as valid operators. It causes a syntax error. Other options are valid expressions with increments.

❓ Predict Output

advanced

Output of complex increment and decrement

What is the output of this C program?

C

int main() {
    int i = 2;
    int j = i++ + --i + i-- + ++i;
    printf("%d\n", j);
    return 0;
}

A 8

B 9

C 10

D 11

💡 Hint

Track the value of i carefully after each increment or decrement.

Start i=2 1) i++ returns 2, i=3 2) --i decrements i to 2, returns 2 3) i-- returns 2, i=1 4) ++i increments i to 2, returns 2 Sum: 2 + 2 + 2 + 2 = 8 So output is 8, option A. Correct answer is C.

❓ Predict Output

expert

Final value after chained increments and decrements

What is the value of variable x after this code runs?

C

int main() {
    int x = 1;
    x = x++ + ++x + --x + x--;
    printf("%d\n", x);
    return 0;
}

A 9

B 7

C 6

D 8

💡 Hint

Evaluate each increment/decrement carefully and update x after each step.

Start x=1 1) x++ returns 1, x=2 2) ++x increments x to 3, returns 3 3) --x decrements x to 2, returns 2 4) x-- returns 2, x=1 Sum: 1 + 3 + 2 + 2 = 8 But x is assigned this sum, so x=8 Option D is 8, so correct answer is C.