Smit04/infixTopostfix,cpp.cpp at main · smitgoyani123/Smit04 · GitHub

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#include <iostream>
using namespace std;
class CharStack {
public:
    char *As;
    int topidx;
    int size;
    CharStack() {
        topidx = -1;
        size = 1;
        As = new char[size];
    }

    void push(char x) {
        if(topidx>=size -1){
            size++;
            char* newArr = new char[size];
            for(int i = 0;i<=topidx;i++)
                newArr[i] = As[i];
            delete[] As;
            As = newArr;
        }
        topidx++;
        As[topidx] = x;
    }

    int pop() {
        if(topidx < 0)
            return '\0';
        else
            return As[topidx--];
    }

    int top() {
        if(topidx < 0)
            return '\0';
        else
            return As[topidx];
    }

    bool isEmpty() {
        if(topidx==-1)
            return true;
        else
            return false;
    }
    ~CharStack(){delete[] As;}
};
int prec(char syb){
    switch(syb){
        case '(':
            return 1;
        case ')':
            return 2;
        case '+':
        case '-':
            return 3;
        case '*':
        case '/':
        case '%':
            return 4;
        case '^':
            return 5;
        default:
            return 0;

    }
}
string infixTopostfix(string s){
    int i=0;
    CharStack st;
    string ans;
    while(i<s.length()){
        if((s[i] >= 'A' && s[i]<='Z') || (s[i] >= 'a' && s[i]<='z') || (s[i] >= '0' && s[i]<='9')){
            ans+=s[i];
        }else if(s[i] == '(')
            st.push(s[i]);
        else if(s[i] == ')') {
            while (!st.isEmpty() && st.top() != '(')
            {
                ans += st.top();
                st.pop();
            }
            st.pop();
        }
        else{
            while(!st.isEmpty() && prec(s[i])<=prec(st.top())){
                ans += st.top();
                st.pop();
            }
            st.push(s[i]);
        }
        i++;
    }
    while (!st.isEmpty())
    {
        ans+=st.top();
        st.pop();
    }

    return ans;
}
int main(){

    string s = "(a+b)*c";

    string str = infixTopostfix(s);
    cout<< str;


    return 0;
}