Used by thousands of developers who passed their interviews
How to Solve Number of Atoms Problem
Master the Number of Atoms LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
Phantom Code generates complete solutions and debugging hints that you can use while explaining your approach, so you stay calm and in control.
undetectable
real-time
works on major platforms
Start Free for WindowsHard#726
LeetCode ProblemNumber of Atoms
Given a string formula representing a chemical formula, return the count of each atom. The atomic element always starts with an uppercase character, then zero or more lowercase letters, representing the name. One or more digits representing that element's count may follow if the count is greater than 1. If the count is 1, no digits will follow. Two formulas are concatenated together to produce another formula. A formula placed in parentheses, and a count (optionally added) is also a formula. Return the count of all elements as a string in the following form: the first name (in sorted order), followed by its count (if that count is more than 1), followed by the second name (in sorted order), followed by its count (if that count is more than 1), and so on. The test cases are generated so that all the values in the output fit in a 32-bit integer.
Hash TableStringStackSorting
Phantom Code will help you solve this problem in real-time during your interview
Get instant solutions, explanations, and code generation
Problem Breakdown
Understanding the Number of Atoms Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
Given a string formula representing a chemical formula, return the count of each atom. The atomic element always starts with an uppercase character, then zero or more lowercase letters, representing the name. One or more digits representing that element's count may follow if the count is greater than 1. If the count is 1, no digits will follow. Two formulas are concatenated together to produce another formula. A formula placed in parentheses, and a count (optionally added) is also a formula. Return the count of all elements as a string in the following form: the first name (in sorted order), followed by its count (if that count is more than 1), followed by the second name (in sorted order), followed by its count (if that count is more than 1), and so on. The test cases are generated so that all the values in the output fit in a 32-bit integer.
HardProblem #726
LeetCodeNumber of Atoms
Related Topics
Hash TableStringStackSorting
How Phantom Code Helps
Get real-time assistance for Number of Atoms problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
formula = "H2O"
Output
"H2O"
# Example 2
Input
formula = "Mg(OH)2"
Output
"H2MgO2"
# Example 3
Input
formula = "K4(ON(SO3)2)2"
Output
"K4N2O14S4"
Constraints
1 <= formula.length <= 1000
formula consists of English letters, digits, '(', and ')'.
formula is always valid.
How Phantom Code Helps with LeetCode Problems
Reinforce undetectability, platform compatibility, and real-time assistance to remove any doubt.
1000+
developers use Phantom Code
and growing every day
95%
success rate
of users pass their interviews
100%
undetectable
native desktop architecture
Real-time
assistance
instant solutions during interviews
See Phantom Code in Action
Watch how Phantom Code helps solve LeetCode problems during live interviews
Start Interview
⌘I
Online Round
⌘O
Hide⌘B
Interview
Listening
Think
Solve Number of Atoms — Given a string formula representing a chemical formula, return the count of each...
Here's the optimal approach using Hash Table:
def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
Start Over ⌘G
Think & Crack ⌘↵
Undetectability Checklist
Run compatibility test before interviews
Use recommended Zoom version settings
Enable advanced screen capture options
Verify native desktop architecture
Test with screen recording software
Platform Compatibility
Zoom
Supported
Google Meet
Supported
HackerRank
Supported
CodeSignal
Supported
CoderPad
Supported
Teams
Supported
User results and traction
Thousands of developers use Phantom Code. Social proof signals that this approach helps real candidates land offers across a range of companies.
Undetectability and technical details
Our native desktop architecture avoids common detection vectors used by browser extensions. We provide a clear checklist so you can run basic checks and confirm the app will be invisible.
Platform compatibility and limitations
We work with Zoom, HackerRank, CodeSignal, CoderPad and other web-based platforms. Check the compatibility note and request a browser link if a specific desktop app is unsupported.
Frequently Asked Questions
Common questions about solving Number of Atoms and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Number of Atoms during interviews?
Phantom Code generates complete solutions instantly with proper complexity analysis, letting you focus on explaining your approach and demonstrating problem-solving skills rather than getting stuck on implementation details during high-pressure situations.
What if the interviewer asks follow-up questions or modifications to problems like Number of Atoms?
Phantom Code adapts in real-time. Screenshot the modified problem or use audio mode to capture the interviewer's follow-up, and get an updated solution within seconds — including edge cases and optimizations.
Can Phantom Code help me communicate my solution for problems like Number of Atoms?
Yes. Phantom Code provides step-by-step approach explanations with 3 progressive thoughts, so you can walk through your solution naturally. It also provides time and space complexity analysis to discuss trade-offs.
How does Phantom Code assist with different programming languages for Number of Atoms type problems?
Phantom Code supports 11 programming languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set your preferred language and get idiomatic solutions.
What coding mistakes does Phantom Code help me avoid during Number of Atoms interviews?
Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
Is Phantom Code detectable when solving problems like Number of Atoms during live interviews?
No. Phantom Code runs as an invisible desktop overlay that doesn't appear in screen shares, recordings, or proctoring software. It works with Zoom, HackerRank, CodeSignal, CoderPad, and all major platforms.
How does Phantom Code help when I'm struggling with Number of Atoms style questions under pressure?
The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
Does Phantom Code work for the coding platforms used in Number of Atoms interviews?
Yes. Phantom Code works with all major coding platforms including LeetCode, HackerRank, CodeSignal, CoderPad, HackerEarth, and any browser-based coding environment.
₹999/month. Zero Detection Cases.
The only AI interview tool with an undetectable desktop overlay, real-time audio listening, and personalized AI responses.