<p>Given a string <code>formula</code> representing a chemical formula, return <em>the count of each atom</em>.</p>

<p>The atomic element always starts with an uppercase character, then zero or more lowercase letters, representing the name.</p>

<p>One or more digits representing that element&#39;s count may follow if the count is greater than <code>1</code>. If the count is <code>1</code>, no digits will follow.</p>

<ul>
	<li>For example, <code>&quot;H2O&quot;</code> and <code>&quot;H2O2&quot;</code> are possible, but <code>&quot;H1O2&quot;</code> is impossible.</li>
</ul>

<p>Two formulas are concatenated together to produce another formula.</p>

<ul>
	<li>For example, <code>&quot;H2O2He3Mg4&quot;</code> is also a formula.</li>
</ul>

<p>A formula placed in parentheses, and a count (optionally added) is also a formula.</p>

<ul>
	<li>For example, <code>&quot;(H2O2)&quot;</code> and <code>&quot;(H2O2)3&quot;</code> are formulas.</li>
</ul>

<p>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 <code>1</code>), followed by the second name (in sorted order), followed by its count (if that count is more than <code>1</code>), and so on.</p>

<p>The test cases are generated so that all the values in the output fit in a <strong>32-bit</strong> integer.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> formula = &quot;H2O&quot;
<strong>Output:</strong> &quot;H2O&quot;
<strong>Explanation:</strong> The count of elements are {&#39;H&#39;: 2, &#39;O&#39;: 1}.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> formula = &quot;Mg(OH)2&quot;
<strong>Output:</strong> &quot;H2MgO2&quot;
<strong>Explanation:</strong> The count of elements are {&#39;H&#39;: 2, &#39;Mg&#39;: 1, &#39;O&#39;: 2}.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> formula = &quot;K4(ON(SO3)2)2&quot;
<strong>Output:</strong> &quot;K4N2O14S4&quot;
<strong>Explanation:</strong> The count of elements are {&#39;K&#39;: 4, &#39;N&#39;: 2, &#39;O&#39;: 14, &#39;S&#39;: 4}.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= formula.length &lt;= 1000</code></li>
	<li><code>formula</code> consists of English letters, digits, <code>&#39;(&#39;</code>, and <code>&#39;)&#39;</code>.</li>
	<li><code>formula</code> is always valid.</li>
</ul>

#include <map>
#include <string>
#include <stack>
#include <cctype>

using namespace std;

class Solution {
public:
    string countOfAtoms(string formula) {
        stack<map<string, int>> stk;
        map<string, int> current;
        int i = 0, n = formula.size();

        while (i < n) {
            if (formula[i] == '(') {
                // Открывающая скобка, сохраняем текущий мап в стек и начинаем новый
                stk.push(current);
                current.clear();
                ++i;
            } else if (formula[i] == ')') {
                // Закрывающая скобка, обрабатываем множитель
                ++i;
                int multiplier = parseNumber(formula, i);
                for (auto& [element, count] : current) {
                    current[element] *= multiplier;
                }
                // Добавляем текущий мап к предыдущему из стека
                map<string, int> temp = stk.top(); stk.pop();
                for (auto& [element, count] : current) {
                    temp[element] += count;
                }
                current = temp;
            } else {
                // Обрабатываем элемент
                string element = parseElement(formula, i);
                int count = parseNumber(formula, i);
                current[element] += count;
            }
        }

        string result;
        for (auto& [element, count] : current) {
            result += element;
            if (count > 1) result += to_string(count);
        }

        return result;
    }

private:
    string parseElement(const string& formula, int& i) {
        string element;
        element += formula[i++]; // Первая буква всегда заглавная
        while (i < formula.size() && islower(formula[i])) {
            element += formula[i++];
        }
        return element;
    }

    int parseNumber(const string& formula, int& i) {
        int num = 0;
        while (i < formula.size() && isdigit(formula[i])) {
            num = num * 10 + (formula[i++] - '0');
        }
        return num == 0 ? 1 : num; // Если числа нет, то возвращаем 1
    }
};

12200