Problem
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Atoms in a Chemical Formula
Certification: Advanced Level
Accuracy: 0%
Submissions: 0
Points: 15
Write a C++ program to count the number of atoms in a valid chemical formula.
Example 1
- Input: formula = "H2O"
- Output: "H:2 O:1"
- Explanation:
- The formula contains two hydrogen atoms and one oxygen atom.
Example 2
- Input: formula = "Mg(OH)2"
- Output: "H:2 Mg:1 O:2"
- Explanation:
- The formula contains:
- One magnesium atom (Mg)
- Two hydrogen atoms (H) - one inside the parentheses multiplied by 2
- Two oxygen atoms (O) - one inside the parentheses multiplied by 2
Constraints
- 1 ≤ formula.length ≤ 1000
- Only valid chemical formulas will be used as input
- Time Complexity: O(n²) where n is the length of the formula
- Space Complexity: O(n)
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Solution Hints
- Use a stack to handle nested parentheses
- Process the formula from right to left or use recursion
- Use a map to store the count of each atom
- Remember to handle the multipliers correctly for atoms inside parentheses
- Sort the output alphabetically according to atom names