Number of Atoms — LeetCode 726 Python Solution
HardStackHash TableStringSorting
- Problem
- #726
- Pattern
- Stack
- Reading time
- 2 min
- Source
- leetcode.com
The problem
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.
Example
- Input
- formula = "H2O"
- Output
- "H2O"
- Explanation
- The count of elements are {'H': 2, 'O': 1}.
Complexity
| Measure | Complexity |
|---|---|
| Time | O(n) |
| Space | O(n) auxiliary |
Pattern: Stack
When the most recent unresolved thing is the one that matters, use a stack. LeetCode 726. Number of Atoms is filed here because LeetCode tags it Stack, which is the vocabulary this hub collects.
The stack guide has the Python template for the pattern and the 194 LeetCode problems that use it.
Related problems
Frequently asked questions
- How hard is LeetCode 726. Number of Atoms?
- LeetCode 726. Number of Atoms is rated Hard on LeetCode.
- What is the time complexity of LeetCode 726. Number of Atoms?
- The Python solution on this page runs in O(n).
- What is the space complexity of LeetCode 726. Number of Atoms?
- The Python solution on this page uses O(n) auxiliary space.
- What topics does LeetCode 726. Number of Atoms cover?
- LeetCode 726. Number of Atoms is tagged Stack, Hash Table, String and Sorting on LeetCode.