<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>

class Solution {
public:
    int pos = 0; 
    string countOfAtoms(string formula) {
        map<string, int> count;
        string curr = "";
        while(pos < formula.length()){
            if(isupper(formula[pos])){
                int start = pos;
                ++pos;
                while(islower(formula[pos])){
                    ++pos;
                }
                int end = pos;
                if(isdigit(formula[pos])){
                    int num = 0;
                    while(isdigit(formula[pos])){
                        num *= 10;
                        num += (formula[pos] - '0');
                        ++pos;
                    }
                    count[formula.substr(start, end - start)] += num;
                } else {
                    count[formula.substr(start, end - start)] ++;
                }
            } 
            else if(formula[pos] == '(') {
                ++pos;
                unordered_map<string, int> temp = countOfEElements(formula);
                int multi = 1;
                if(isdigit(formula[pos])){
                    int num = 0;
                    while(isdigit(formula[pos])){
                        num *= 10;
                        num += (formula[pos] - '0');
                        ++pos;
                    }
                    multi = num;
                }
                for(auto & tmp : temp){
                    count[tmp.first] += (tmp.second * multi);
                }
            } else if(formula[pos] == ')'){
                ++pos;
                break;
            } 
            else
                ++pos;
        }
        string res = "";
        for(auto& cnt : count){
            res += cnt.first;
            if(cnt.second > 1) res += to_string(cnt.second);
        }
        return res;
    }
    unordered_map<string, int> countOfEElements(string& formula){
        unordered_map<string, int> count;
        while(pos < formula.length()){
            if(isupper(formula[pos])){
                int start = pos;
                ++pos;
                while(islower(formula[pos])){
                    ++pos;
                }
                int end = pos;
                if(isdigit(formula[pos])){
                    int num = 0;
                    while(isdigit(formula[pos])){
                        num *= 10;
                        num += (formula[pos] - '0');
                        ++pos;
                    }
                    count[formula.substr(start, end - start)] += num;
                } else {
                    count[formula.substr(start, end - start)] ++;
                }
            } 
            else if(formula[pos] == '(') {
                ++pos;
                unordered_map<string, int> temp = countOfEElements(formula);
                int multi = 1;
                if(isdigit(formula[pos])){
                    int num = 0;
                    while(isdigit(formula[pos])){
                        num *= 10;
                        num += (formula[pos] - '0');
                        ++pos;
                    }
                    multi = num;
                }
                for(auto & tmp : temp){
                    count[tmp.first] += (tmp.second * multi);
                }
            } else if(formula[pos] == ')'){
                ++pos;
                break;
            } 
            else
                ++pos;
        }
        return count;
    }
};
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