tomatocream
1dec88aaf2
Add populate-notes.mjs that fetches problem descriptions and Python/C++ code stubs from LeetCode's GraphQL API. Populated all 197 NeetCode 150 note files with: - Problem description (examples, constraints) - Python code stub (function signature) - C++ code stub (function signature + includes) API responses cached in leetcode/.cache/leetcode/ for instant re-runs.
2.1 KiB
TODO 0726. Number of Atoms hard
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.
- For example,
"H2O"and"H2O2"are possible, but"H1O2"is impossible.
Two formulas are concatenated together to produce another formula.
- For example,
"H2O2He3Mg4"is also a formula.
A formula placed in parentheses, and a count (optionally added) is also a formula.
- For example,
"(H2O2)"and"(H2O2)3"are formulas.
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.
Example 1:
Input: formula = "H2O"
Output: "H2O"
Explanation: The count of elements are {'H': 2, 'O': 1}.Example 2:
Input: formula = "Mg(OH)2"
Output: "H2MgO2"
Explanation: The count of elements are {'H': 2, 'Mg': 1, 'O': 2}.Example 3:
Input: formula = "K4(ON(SO3)2)2"
Output: "K4N2O14S4"
Explanation: The count of elements are {'K': 4, 'N': 2, 'O': 14, 'S': 4}.Constraints:
1 <= formula.length <= 1000formulaconsists of English letters, digits,'(', and')'.formulais always valid.
TODO Approach
Write your approach here.
TODO Python
class Solution:
def countOfAtoms(self, formula: str) -> str:TODO C++
class Solution {
public:
string countOfAtoms(string formula) {
}
};