Else–if ladder in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an else-if ladder in C++?

An else-if ladder is a series of if-else statements used to check multiple conditions one after another. It helps decide which block of code to run based on different conditions.

beginner

How does the else-if ladder work in C++?

The program checks each if or else-if condition from top to bottom. When it finds a true condition, it runs that block and skips the rest.

beginner

Write a simple else-if ladder to check if a number is positive, negative, or zero.

Example: int num = 5; if (num > 0) { // positive } else if (num < 0) { // negative } else { // zero }

intermediate

Why use else-if ladder instead of multiple if statements?

Else-if ladder stops checking conditions once one is true, making the program faster and avoiding running multiple blocks when only one should run.

beginner

Can else-if ladder have an else block? What is its purpose?

Yes, the else block runs if none of the if or else-if conditions are true. It acts as a default case.

What happens when an else-if condition is true in a ladder?

A Only the last block runs

B All blocks run regardless

C The program crashes

D The corresponding block runs and the rest are skipped

In an else-if ladder, once a true condition is found, its block runs and the rest are skipped.

Which keyword starts an else-if ladder in C++?

A elif

B else if

C elseif

D else

The correct syntax in C++ is 'else if' with a space.

What is the role of the else block in an else-if ladder?

A Runs only if the first condition is true

B Runs before all conditions

C Runs if no previous condition is true

D Is optional and never runs

The else block runs only if all previous if and else-if conditions are false.

Why is an else-if ladder more efficient than multiple separate if statements?

A It stops checking after the first true condition

B It runs all conditions faster

C It uses less memory

D It allows multiple blocks to run

Else-if ladder stops checking conditions once one is true, saving time.

Which of these is a correct else-if ladder syntax in C++?

A if (x>0) {} else if (x<0) {} else {}

B if (x>0) {} elseif (x<0) {} else {}

C if (x>0) {} else (x<0) {} else {}

D if (x>0) {} else if(x<0) else {}

Option A uses correct syntax with 'else if' and proper braces.

Explain how an else-if ladder controls program flow in C++.

Think about how the program decides which code to run based on conditions.

Write a simple else-if ladder to classify a number as positive, negative, or zero.

Use if, else if, and else keywords with comparison operators.

Practice

1.

What does an else-if ladder do in C++?

easy

A. Skips all conditions and runs the else block always

B. Runs all conditions regardless of their truth

C. Only runs the last condition in the ladder

D. Checks multiple conditions one by one and runs the first true block

Solution

1. Step 1: Understand the purpose of else-if ladder

   An else-if ladder is used to check multiple conditions in order, one after another.

2. Step 2: Identify how conditions are evaluated

   It runs the code block for the first condition that is true and skips the rest.

3. Final Answer:

   Checks multiple conditions one by one and runs the first true block -> Option D

4. Quick Check:

   Else-if ladder = first true condition runs [OK]

Hint: Remember: else-if stops at first true condition [OK]

Common Mistakes:

• Thinking all conditions run
• Believing else always runs
• Confusing else-if with separate ifs

2.

Which of the following is the correct syntax for an else-if ladder in C++?

int x = 10;
if (x < 5) {
  // code A
} _____ (x < 15) {
  // code B
} else {
  // code C
}

easy

A. else if

B. elseif

C. else_if

D. else if()

Solution

1. Step 1: Recall correct else-if syntax in C++

   The correct keyword is else if with a space, no underscores or parentheses after else.

2. Step 2: Check each option

   Options A, B, and C are invalid syntax in C++.

3. Final Answer:

   else if -> Option A

4. Quick Check:

   Correct syntax = else if [OK]

Hint: Use 'else if' with space, no underscores or parentheses [OK]

Common Mistakes:

• Writing 'elseif' as one word
• Using underscores like 'else_if'
• Adding parentheses after else

3.

What will be the output of this C++ code?

int num = 7;
if (num > 10) {
  std::cout << "Greater than 10";
} else if (num > 5) {
  std::cout << "Greater than 5";
} else {
  std::cout << "5 or less";
}

medium

A. Greater than 5

B. 5 or less

C. Greater than 10

D. No output

Solution

1. Step 1: Evaluate first condition (num > 10)

   7 is not greater than 10, so this block is skipped.

2. Step 2: Evaluate second condition (num > 5)

   7 is greater than 5, so this block runs and prints "Greater than 5".

3. Final Answer:

   Greater than 5 -> Option A

4. Quick Check:

   7 > 5 = true, prints "Greater than 5" [OK]

Hint: Check conditions top to bottom, first true runs [OK]

Common Mistakes:

• Choosing first condition output incorrectly
• Ignoring else-if order
• Assuming else runs always

4.

Find the error in this else-if ladder code snippet:

int score = 85;
if (score >= 90) {
  std::cout << "Grade A";
} else if score >= 80 {
  std::cout << "Grade B";
} else {
  std::cout << "Grade C";
}

medium

A. Missing semicolon after std::cout

B. Missing parentheses around condition in else-if

C. Incorrect use of else instead of else-if

D. Using >= instead of >

Solution

1. Step 1: Check syntax of else-if condition

   In C++, conditions must be inside parentheses. The else-if line lacks parentheses.

2. Step 2: Verify other parts

   Semicolons and operators are correct; only parentheses are missing.

3. Final Answer:

   Missing parentheses around condition in else-if -> Option B

4. Quick Check:

   Conditions need parentheses [OK]

Hint: Always put conditions inside parentheses [OK]

Common Mistakes:

• Forgetting parentheses in if/else-if
• Missing semicolons after statements
• Confusing else and else-if syntax

5.

Write an else-if ladder to print the day of the week given an integer day (1 to 7). What will be printed if day = 5?

int day = 5;
if (day == 1) {
  std::cout << "Monday";
} else if (day == 2) {
  std::cout << "Tuesday";
} else if (day == 3) {
  std::cout << "Wednesday";
} else if (day == 4) {
  std::cout << "Thursday";
} else if (day == 5) {
  std::cout << "Friday";
} else if (day == 6) {
  std::cout << "Saturday";
} else if (day == 7) {
  std::cout << "Sunday";
} else {
  std::cout << "Invalid day";
}

hard

A. Thursday

B. Saturday

C. Friday

D. Invalid day

Solution

1. Step 1: Match the value of day with conditions

   day is 5, so the else-if condition day == 5 is true.

2. Step 2: Identify the output for day == 5

   The code prints "Friday" for day 5.

3. Final Answer:

   Friday -> Option C

4. Quick Check:

   day 5 = Friday [OK]

Hint: Match day number to correct else-if condition [OK]

Common Mistakes:

• Mixing up day numbers and names
• Forgetting else block for invalid days
• Using wrong comparison operators