Nested conditional statements in Go - Time & Space Complexity

Time Complexity: Nested conditional statements

O(1)

Understanding Time Complexity

When we use nested conditional statements, we want to know how they affect the time it takes for the program to run.

We ask: Does adding more conditions make the program slower as input grows?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

func checkNumber(n int) string {
    if n > 0 {
        if n % 2 == 0 {
            return "Positive even"
        } else {
            return "Positive odd"
        }
    } else if n < 0 {
        return "Negative"
    } else {
        return "Zero"
    }
}

This code checks if a number is positive, negative, or zero, and if positive, whether it is even or odd.

Identify Repeating Operations

Look for loops or repeated checks that happen many times.

• Primary operation: Simple conditional checks (if-else).
• How many times: Each check runs once per function call.

How Execution Grows With Input

The number of steps does not increase when the input number gets bigger.

Input Size (n)	Approx. Operations
10	3 checks
100	3 checks
1000	3 checks

Pattern observation: The time stays the same no matter how big the number is.

Final Time Complexity

Time Complexity: O(1)

This means the program takes the same amount of time no matter the input size.

Common Mistake

[X] Wrong: "More conditions always make the program slower as input grows."

[OK] Correct: These conditions run only once per input, so they do not slow down the program as input size increases.

Interview Connect

Understanding how nested conditions affect time helps you explain your code clearly and shows you know when performance matters.

Self-Check

"What if we added a loop inside the nested conditions that runs n times? How would the time complexity change?"

Practice

1.

What does a nested conditional statement in Go allow you to do?

Example: if x > 0 { if x < 10 { ... } }

easy

A. Declare multiple variables in one line

B. Run multiple loops at the same time

C. Check one condition inside another condition

D. Create a function inside another function

Solution

1. Step 1: Understand the structure of nested conditionals

   A nested conditional means putting one if statement inside another to check multiple conditions step by step.

2. Step 2: Identify the purpose of the example code

   The example checks if x is greater than 0, then inside that block checks if x is less than 10.

3. Final Answer:

   Check one condition inside another condition -> Option C

4. Quick Check:

   Nested conditionals = conditions inside conditions [OK]

Hint: Nested means inside another condition [OK]

Common Mistakes:

• Confusing nested conditionals with loops
• Thinking nested means multiple variables
• Mixing nested conditionals with function declarations

2.

Which of the following is the correct syntax for a nested if statement in Go?

if x > 0 {
    if x < 10 {
        fmt.Println("x is between 1 and 9")
    }
}

easy

A. if x > 0 {
if x < 10 {
fmt.Println("x is between 1 and 9")
}
}

B. if x > 0
if x < 10
fmt.Println("x is between 1 and 9")

C. if (x > 0) then if (x < 10) { fmt.Println("x is between 1 and 9") }

D. if x > 0 {
if x < 10 {
fmt.Println("x is between 1 and 9")
}
}

Solution

1. Step 1: Check Go syntax for nested if

   Go requires braces {} around blocks and proper indentation for readability.

2. Step 2: Compare options with correct syntax

   if x > 0 { if x < 10 { fmt.Println("x is between 1 and 9") } } uses braces and indentation correctly, matching Go style.

3. Final Answer:

   if x > 0 { if x < 10 { fmt.Println("x is between 1 and 9") } } -> Option A

4. Quick Check:

   Correct braces and indentation = if x > 0 { if x < 10 { fmt.Println("x is between 1 and 9") } } [OK]

Hint: Use braces {} and indent nested if blocks [OK]

Common Mistakes:

• Omitting braces {} around if blocks
• Using incorrect keywords like 'then'
• Not indenting nested blocks properly

3.

What will be the output of this Go code?

package main
import "fmt"
func main() {
    x := 7
    if x > 5 {
        if x < 10 {
            fmt.Println("A")
        } else {
            fmt.Println("B")
        }
    } else {
        fmt.Println("C")
    }
}

medium

A. B

B. No output

C. C

D. A

Solution

1. Step 1: Evaluate the first condition (x > 5)

   x is 7, which is greater than 5, so the first if block runs.

2. Step 2: Evaluate the nested condition (x < 10)

   7 is less than 10, so it prints "A" inside the nested if.

3. Final Answer:

   A -> Option D

4. Quick Check:

   7 > 5 and 7 < 10 = "A" [OK]

Hint: Check conditions stepwise from outer to inner [OK]

Common Mistakes:

• Ignoring nested else block
• Confusing output with 'B' or 'C'
• Assuming no output if conditions fail

4.

Find the error in this Go code snippet:

package main
import "fmt"
func main() {
    x := 3
    if x > 0
        if x < 5 {
            fmt.Println("x is between 1 and 4")
        }
}

medium

A. Missing import statement for fmt

B. Missing braces {} around the first if block

C. Incorrect variable declaration for x

D. Using > and < instead of > and <

Solution

1. Step 1: Check syntax of the first if statement

   The first if statement lacks braces {} and a closing brace for the block.

2. Step 2: Understand Go requires braces for if blocks

   In Go, if statements must have braces {} even if the block is one line or nested.

3. Final Answer:

   Missing braces {} around the first if block -> Option B

4. Quick Check:

   Go if statements need braces {} [OK]

Hint: Always use braces {} for if blocks in Go [OK]

Common Mistakes:

• Forgetting braces {} on if statements
• Thinking > and < must be escaped
• Assuming import fmt is missing

5.

Write a nested conditional in Go that prints "Small positive" if a number n is greater than 0 and less than 10, prints "Large positive" if it is 10 or more, and prints "Non-positive" otherwise. What is the correct code?

hard

A. if n > 0 {
if n < 10 {
fmt.Println("Small positive")
} else {
fmt.Println("Large positive")
}
} else {
fmt.Println("Non-positive")
}

B. if n > 0 && n < 10 {
fmt.Println("Small positive")
} else if n > 10 {
fmt.Println("Large positive")
} else {
fmt.Println("Non-positive")
}

C. if n <= 10 {
if n > 0 {
fmt.Println("Small positive")
} else {
fmt.Println("Non-positive")
}
} else {
fmt.Println("Large positive")
}

D. if n > 0 {
if n > 10 {
fmt.Println("Large positive")
} else {
fmt.Println("Small positive")
}
} else {
fmt.Println("Non-positive")
}

Solution

1. Step 1: Understand the conditions to check

   We check if n is greater than 0 first, then inside that check if n is less than 10 for "Small positive" or else "Large positive".

2. Step 2: Match the nested conditional structure

   if n > 0 { if n < 10 { fmt.Println("Small positive") } else { fmt.Println("Large positive") } } else { fmt.Println("Non-positive") } correctly nests the second if inside the first and prints the right messages for each case.

3. Final Answer:

   if n > 0 { if n < 10 { fmt.Println("Small positive") } else { fmt.Println("Large positive") } } else { fmt.Println("Non-positive") } -> Option A

4. Quick Check:

   Nested if for ranges = if n > 0 { if n < 10 { fmt.Println("Small positive") } else { fmt.Println("Large positive") } } else { fmt.Println("Non-positive") } [OK]

Hint: Check outer condition first, then inner for ranges [OK]

Common Mistakes:

• Swapping conditions order
• Using else if instead of nested if
• Mixing up the printed messages