Assignment operators in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of compound assignment with multiplication

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    int a = 5;
    a *= 3 + 2;
    std::cout << a << std::endl;
    return 0;
}

A Syntax error

B 25

C 15

D 10

💡 Hint

Remember operator precedence: multiplication assignment and addition.

The expression 'a *= 3 + 2;' is evaluated as 'a *= (3 + 2);' because '+' has higher precedence than '*='. So, a = 5 * 5 = 25.

❓ Predict Output

intermediate

Result of chained assignment

What is the value of variable c after running this code?

C++

#include <iostream>
int main() {
    int a, b, c;
    a = b = c = 7;
    c += 3;
    std::cout << c << std::endl;
    return 0;
}

A 7

B 3

C 10

D 0

💡 Hint

Look at the chained assignment and then the addition assignment.

All variables a, b, and c are assigned 7. Then c is increased by 3, so c becomes 10.

❓ Predict Output

advanced

Effect of bitwise assignment operator

What is the output of this C++ program?

C++

#include <iostream>
int main() {
    unsigned int x = 12; // binary 1100
    x >>= 2;
    std::cout << x << std::endl;
    return 0;
}

A 3

B 48

C 6

D Syntax error

💡 Hint

Right shift operator divides by powers of two.

Right shifting 12 (1100 binary) by 2 bits results in 3 (0011 binary).

❓ Predict Output

advanced

Output of combined assignment with logical operators

What is the output of this code snippet?

C++

#include <iostream>
int main() {
    int a = 5;
    a &= 3;
    std::cout << a << std::endl;
    return 0;
}

A 0

B 7

C 1

D 2

💡 Hint

Use bitwise AND on the binary forms of 5 and 3.

5 in binary is 0101, 3 is 0011. Bitwise AND is 0001 which is 1.

🧠 Conceptual

expert

Understanding behavior of assignment in expressions

Consider this code snippet. What is the value of y after execution?

C++

#include <iostream>
int main() {
    int x = 4;
    int y = (x += 3) * 2;
    std::cout << y << std::endl;
    return 0;
}

A 14

B 10

C 8

D 7

💡 Hint

Remember that assignment expressions return the assigned value.

x += 3 changes x to 7 and returns 7. Then y = 7 * 2 = 14.

Practice

1. Which of the following assignment operators adds the right value to the left variable and stores the result back in the left variable?

easy

A. +=

B. =

C. -=

D. *=

Solution

1. Step 1: Understand the meaning of +=

   The operator += adds the right side value to the left side variable and updates the variable with the new value.

2. Step 2: Compare with other operators

   = assigns a value, -= subtracts, and *= multiplies. Only += adds and assigns.

3. Final Answer:

   += -> Option A

4. Quick Check:

   Add and assign = += [OK]

Hint: Remember: += means add then assign [OK]

Common Mistakes:

• Confusing = with +=
• Thinking -= adds values
• Mixing *= with addition

2. Which of the following is the correct syntax to multiply variable x by 5 and store the result back in x?

easy

A. x =* 5;

B. x *= 5;

C. x = 5*;

D. x = 5 *;

Solution

1. Step 1: Identify the correct assignment operator syntax

   The operator to multiply and assign is *=, so x *= 5; is correct.

2. Step 2: Check other options for syntax errors

   x =* 5; and x = 5*; are invalid syntax. x = 5 *; is incomplete.

3. Final Answer:

   x *= 5; -> Option B

4. Quick Check:

   Multiply and assign = *= [OK]

Hint: Use operator before = for combined assignment [OK]

Common Mistakes:

• Placing * after = instead of before
• Leaving incomplete expressions
• Confusing with simple assignment =

3. What is the output of the following code?

int a = 10;
a += 5;
a -= 3;
std::cout << a;

medium

A. 12

B. 15

C. 8

D. 10

Solution

1. Step 1: Calculate a += 5;

   Starting with a = 10, adding 5 gives a = 15.

2. Step 2: Calculate a -= 3;

   Subtracting 3 from 15 gives a = 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   10 + 5 - 3 = 12 [OK]

Hint: Apply each assignment step by step [OK]

Common Mistakes:

• Adding and subtracting in wrong order
• Confusing += and -= effects
• Ignoring the updated value after first operation

4. Identify the error in the following code snippet:

int x = 7;
x =+ 3;
std::cout << x;

medium

A. Syntax error due to incorrect operator

B. x will be 10

C. x will be 3

D. No error, output is 10

Solution

1. Step 1: Analyze x =+ 3;

   This is not the addition assignment +=. Instead, =+ means assign positive 3 to x.

2. Step 2: Determine the value of x after assignment

   x becomes 3, not 10, because =+ is just assignment with unary plus.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   =+ is assignment, not addition [OK]

Hint: Watch for =+ vs += difference [OK]

Common Mistakes:

• Confusing =+ with += operator
• Expecting addition instead of assignment
• Assuming output is sum without checking syntax

5. Given int n = 20;, which code snippet correctly divides n by 4 and then subtracts 2 from the result, updating n accordingly?

hard

A. n = n - 2 / 4;

B. n -= 2; n /= 4;

C. n = (n - 2) / 4;

D. n /= 4; n -= 2;

Solution

1. Step 1: Understand the required operations order

   First divide n by 4, then subtract 2 from the result, updating n each time.

2. Step 2: Check each option

   n /= 4; n -= 2; does n /= 4; then n -= 2;, matching the requirement. n -= 2; n /= 4; reverses order. n = (n - 2) / 4; subtracts first due to parentheses (18 / 4 = 4). n = n - 2 / 4; subtracts incorrectly.

3. Step 3: Confirm correct update

   n /= 4; n -= 2; updates n stepwise as requested.

4. Final Answer:

   n /= 4; n -= 2; -> Option D

5. Quick Check:

   Divide then subtract = n /= 4; n -= 2; [OK]

Hint: Follow operation order exactly [OK]

Common Mistakes:

• Reversing operation order
• Misunderstanding combined expressions
• Incorrect operator precedence assumptions