Today was my Microsoft R1 (DSA) interview for an SSE role.

It didn’t go well. I couldn’t solve the questions.

But instead of hiding it, I’m documenting everything in detail so others can prepare better. If this helps even one person crack it, it’s worth it.

❌ Question 1: Next Bigger Number with Same Digits

🔹 Problem Statement

Given a positive integer N, return the immediate next greater number that can be formed using the same digits.

If no such number exists, return the same number.

🔹 Examples

Input: 123
Output: 132

Input: 321
Output: 321   (no bigger permutation exists)

Input: 115
Output: 151

Input: 218765
Output: 251678

Input: 534976
Output: 536479

🔹 Edge Cases They Expect You to Think About

• Repeated digits → 115 → 151
• Already maximum permutation → 987 → 987
• Single digit → 7 → 7
• Large input (should be efficient, not brute force)

🔹 What They Were Testing

• Understanding of Next Permutation algorithm
• In-place manipulation
• Handling edge cases cleanly

❌ Question 2: Implement ftoa (Float to String)

🔹 Problem Statement

Write a function ftoa() that converts a given floating-point number to a string without using standard library conversion functions.

You are given:

• A float num
• An integer precision (number of digits after decimal)

Return the string representation of the number up to the given precision.

🔹 Function Signature (conceptual)

ftoa(num, precision) -> string

🔹 Examples

Input: num = 1.555, precision = 2
Output: "1.55"

Input: num = 1.555, precision = 0
Output: "1"

Input: num = 123.4, precision = 3
Output: "123.400"

Input: num = -12.3456, precision = 2
Output: "-12.34"

🔹 Edge Cases

• Negative numbers
• Precision = 0
• Leading/trailing zeros
• Floating precision issues (very important)
• Large integer part

🔹 What They Were Testing

• Number manipulation

• Handling floating precision manually

• Attention to detail

• Ability to break problem into:

  • Integer part
  • Fractional part

💭 Where I Struggled

• I couldn’t quickly recall the structured approach for next permutation
• For ftoa, I got stuck handling the fractional part cleanly
• Most importantly, I lost momentum mid-way

🔥 What I Learned

• Knowing ≠ Performing
• Practice under timed + pressure conditions is crucial
• Always talk through your approach, even if incomplete

🚀 Final Note

Yes, I failed this round.

But I’m not stopping here.

I have my next round scheduled, and I’ll show up again—better prepared, more aware, and mentally stronger.

If you’re preparing for Microsoft:

👉 Don’t just solve problems — simulate interviews
👉 Don’t just read solutions — explain them out loud
👉 Don’t avoid failure — learn from it fast

This is just one bad round. Not the end.
See you on the other side 💯