<p>Given a string <code>s</code> representing a valid expression, implement a basic calculator to evaluate it, and return <em>the result of the evaluation</em>.</p>

<p><strong>Note:</strong> You are <strong>not</strong> allowed to use any built-in function which evaluates strings as mathematical expressions, such as <code>eval()</code>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;1 + 1&quot;
<strong>Output:</strong> 2
</pre>

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

<pre>
<strong>Input:</strong> s = &quot; 2-1 + 2 &quot;
<strong>Output:</strong> 3
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;(1+(4+5+2)-3)+(6+8)&quot;
<strong>Output:</strong> 23
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 3 * 10<sup>5</sup></code></li>
	<li><code>s</code> consists of digits, <code>&#39;+&#39;</code>, <code>&#39;-&#39;</code>, <code>&#39;(&#39;</code>, <code>&#39;)&#39;</code>, and <code>&#39; &#39;</code>.</li>
	<li><code>s</code> represents a valid expression.</li>
	<li><code>&#39;+&#39;</code> is <strong>not</strong> used as a unary operation (i.e., <code>&quot;+1&quot;</code> and <code>&quot;+(2 + 3)&quot;</code> is invalid).</li>
	<li><code>&#39;-&#39;</code> could be used as a unary operation (i.e., <code>&quot;-1&quot;</code> and <code>&quot;-(2 + 3)&quot;</code> is valid).</li>
	<li>There will be no two consecutive operators in the input.</li>
	<li>Every number and running calculation will fit in a signed 32-bit integer.</li>
</ul>

class Solution {
public:
    int calculate(string s) {
        string str = "";
        int n = s.size();

        bool isAny = false;
        for(int i = 0; i < n; i++){
            if(s[i] != ' '){
                str += s[i];
            }
            if(s[i] == '+' || s[i] == '-' || s[i] == '(' || s[i] == ')'){
                isAny = true;
            }
        }
        if(isAny == false){
        //    reverse(str.begin(), str.end());
           cout << "sd" << endl;
           long long v = stol(str);
            return stol(str);
        }
        n = str.size();
        cout << str << " " << n << endl;
        string mp[300001];
        string arr[300001];

        int fpointer = 0;

        for(int i = 0; i < n; i++){
            //cout << fpointer << endl;
            if(str[i] == '+'){
                fpointer++;
                arr[fpointer] = "+";
            }
            else if(str[i] == '-'){
                fpointer++;
                arr[fpointer] = "-";
            }
            else if(str[i] == '('){
                fpointer++;
                arr[fpointer] = "(";

            }
            else if(str[i] == ')'){
                stack<string>st;
                // cout << "here" << endl;
                while(1){
                    if(arr[fpointer] == "("){
                        fpointer--;
                        break;
                    }
                    // cout << arr[fpointer] << " ";
                    st.push(arr[fpointer]);
                    fpointer--;
                }
                int cal = 0;
                if(st.top() == "-"){
                    cal = -1;
                    st.pop();
                    string v = st.top();
                    cal = -1 * stoi(v);
                    st.pop();
                }
                else{
                    string v = st.top();
                st.pop();
                cal = stoi(v);
                }
                string sign = "+";
                while(!st.empty()){
                    string currentV = st.top();
                    st.pop();
                    if(currentV == "+"){
                        sign = "+";
                    }
                    else if(currentV == "-"){
                        sign = "-";
                    }
                    else{
                        if(sign == "+"){
                            cal += stoi(currentV);
                        }
                        else{
                            cal -= stoi(currentV);
                        }
                    }
                }
                fpointer++;
                arr[fpointer] = to_string(cal);
            }
            else{
                int num = 0;
                while(1){
                    if(i == n){
                        break;
                    }
                    if(str[i] == '+' || str[i] == '-' || str[i] == '(' || str[i] == ')'){
                        i--;
                        break;
                    }
                    int digit = str[i]-'0';
                    num = num * 10 + digit;
                    i++;
                }
                fpointer++;
                arr[fpointer] = to_string(num);
                
            }
        }

        stack<string>st;

        for(int i = fpointer; i >= 1; i--){
            st.push(arr[i]);
        }

        long long cal = 0;
        if(st.top() == "-"){
            cal = -1;
            st.pop();
            string v = st.top();
            cal = -1 * stoi(v);
            st.pop();
        }
        else{
            string v = st.top();
            st.pop();
            cal = stoi(v);
        }
        string sign = "+";
        while(!st.empty()){
            string currentV = st.top();
            st.pop();
            if(currentV == "+"){
                sign = "+";
            }
            else if(currentV == "-"){
                sign = "-";
            }
            else{
                if(sign == "+"){
                    cal += stoll(currentV);
                }
                else{
                    cal -= stoi(currentV);
                }
            }
        }

        return cal;
    }
};
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