Answers for "infix to postfix conversion c++"

infix to postfix program in c++

/*https://github.com/Sudhanshu1304/Stack-Application*/

#include <iostream>
#include<string>
using namespace std;



class Stack{


private:


    char A[5];
    int Size;

public:
    int top;
    Stack(){

        top=-1;
        Size=sizeof(A)/sizeof(char);

    }



    bool IsFull(){

        if(top==Size-1){
            return true;
        }
        else{
            return false;
        }
    }

    bool IsEmpty(){

        if(top==-1){
            return true;
        }
        else{
            return false;
        }
    }

    char peek(){

        return A[top];
    }

    void Push(char val){

        if (IsFull()==false){
            top++;
            A[top]=val;
        }
        else{
            cout<<"\nThe Stack is Full"<<endl;
        }
    }

    char Pop(){

        if(IsEmpty()==false){
            char temp=A[top];
            A[top]='0';
            top--;
            return temp;
        }
        else{
            return '-1';
        }

    }

    void Show_Stack(){


        for(int i=0;i<top+1;i++){
            cout<<A[i];
        }


    }

};


int Search(char A){


    string CHAR[]={"([","{)","]}","+-","*/","^$"};
    int Size=(sizeof(CHAR)/sizeof(string));

    for(int i=0;i<Size;i++){

        if(A==CHAR[i][0]){
                if(i+i>=6){
                    return i+i;
                }
                else{
                    return i+i+0;
                }

        }
        else if(CHAR[i][1]==A){
             if(i+i>=6){
                    return i+i;
                }
                else{
                    return i+i+1;
                }
        }
    }
    return -1;

}




void Display(char ch,string vari, Stack &s){

    int Size=s.top+1;


    cout<<"\n   "<<ch<<"           ";
    s.Show_Stack();
    for(int i=0;i<10-Size;i++){
        cout<<" ";
    }
    cout<<vari<<endl;

}


int main(){

    Stack STACK;
    char temp;
    string exp;//"A+B*C";
    cout<<"Enter Your Expression :";
    cin>>exp;

    string out="";
    cout<<"\n\nExpression   Stack   Postfix\n"<<endl;
    for(int i=0;i<exp.size();i++){

        temp=exp[i];

        int ab=Search(temp);

        if (ab!=-1){

            /* If We ENCOUNTER CLOSING BRACKETS*/
            if(ab<=5 && ab>=3){



                while(Search(STACK.peek())>2){
                    char val=STACK.Pop();
                        out=out+val;

                    Display(temp,out,STACK);
                }
                STACK.Pop();
                Display(temp,out,STACK);
                }
            /* Search Precedence*/
            else{
                if (Search(temp)>=0 && Search(temp)<=2){
                    STACK.Push(temp);
                    Display(temp,out,STACK);
                }

                /* If TOP < Temp */

                else if(Search(STACK.peek())<ab){

                        STACK.Push(temp);
                        Display(temp,out,STACK);
                }
                else{
                    /* if STACK= +,* and temp= + then we have to remove two times */


                    while(Search(STACK.peek())>=ab){

                        char val=STACK.Pop();
                            out=out+val;
                        Display(temp,out,STACK);
                    }
                    STACK.Push(temp);
                    Display(temp,out,STACK);
                }
            }
        }
        /* If an Alphabet */
        else{

            out=out+temp;
            Display(temp,out,STACK);

            }


    }
    while(STACK.IsEmpty()==false){

        char val=STACK.Pop();

            out=out+val;
        Display(temp,out,STACK);

    }
    cout<<"\n\nFINAL STRING : "<<out<<endl;


}

infix to postfix conversion

Best Solution
-------------------------------------------------------------------
#include<bits/stdc++.h>
using namespace std;

int prec(char c) {
    if(c == '^') {
        return 3;
    }
    else if(c == '*' || c == '/') {
        return 2;
    }
    else if(c == '+' || c =='-') {
        return 1;
    }
    else {
        return -1;
    }
}

string infixToPostfix(string s) {
    stack<char> st;
    string res;

    for (int i = 0; i < s.length(); i++)
    {
        if((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')) {
            res += s[i];
        }
        else if(s[i] == '(') {
            st.push(s[i]);
        }
        else if(s[i] == ')') {
            while (!st.empty() && st.top() != '(')
            {
                res += st.top();
                st.pop();
            }
            if(!st.empty()) {
                st.pop(); // Popping '(' here
            }
        }
        else {
            while (!st.empty() && prec(st.top()) >= prec(s[i]))
            {
                res += st.top();
                st.pop();
            }
            st.push(s[i]);
        }
    }
    
    while (!st.empty())
    {
       res += st.top();
       st.pop();
    }
    
    return res;
}

int main() {
    string exp = "a+b*(c^d-e)^(f+g*h)-i";
    cout<<infixToPostfix(exp);
    return 0;
}

infix to postfix conversion c++

//Easiet way to solve infix to postfix expression
bool isOperator(char c)
{
	if(c=='+'||c=='-'||c=='*'||c=='/'||c=='^')
	{
		return true;
	}
	else
	{
		return false;
	}
}

int precedence(char c) 
{ 
    if(c == '^') 
    return 3; 
    else if(c == '*' || c == '/') 
    return 2; 
    else if(c == '+' || c == '-') 
    return 1; 
    else
    return -1; 
} 

string InfixToPostfix(stack<char> s, string infix)
{
	string postfix;
	for(int i=0;i<infix.length();i++)
	{
		if((infix[i] >= 'a' && infix[i] <= 'z')
		||(infix[i] >= 'A' && infix[i] <= 'Z'))
		{
			postfix+=infix[i];
		}
		else if(infix[i] == '(')
		{
			s.push(infix[i]);
		}
		else if(infix[i] == ')')
		{
			while((s.top()!='(') && (!s.empty()))
			{
				char temp=s.top();
				postfix+=temp;
				s.pop();
			}
			if(s.top()=='(')
			{
				s.pop();
			}
		}
		else if(isOperator(infix[i]))
		{
			if(s.empty())
			{
				s.push(infix[i]);
			}
			else
			{
				if(precedence(infix[i])>precedence(s.top()))
				{
					s.push(infix[i]);
				}	
				else if((precedence(infix[i])==precedence(s.top()))&&(infix[i]=='^'))
				{
					s.push(infix[i]);
				}
				else
				{
					while((!s.empty())&&( precedence(infix[i])<=precedence(s.top())))
					{
						postfix+=s.top();
						s.pop();
					}
					s.push(infix[i]);
				}
			}
		}
	}
	while(!s.empty())
	{
		postfix+=s.top();
		s.pop();
	}
	
	return postfix;
}

int main() 
{  

  	string infix_exp, postfix_exp;
  	cout<<"Enter a Infix Expression :"<<endl;
  	cin>>infix_exp;
  	stack <char> stack;
	cout<<"INFIX EXPRESSION: "<<infix_exp<<endl;
  	postfix_exp = InfixToPostfix(stack, infix_exp);
  	cout<<endl<<"POSTFIX EXPRESSION: "<<postfix_exp;
	  
	return 0;
}

infix to postfix conversion

Begin
   initially push some special character say # into the stack
   for each character ch from infix expression, do
      if ch is alphanumeric character, then
         add ch to postfix expression
      else if ch = opening parenthesis (, then
         push ( into stack
      else if ch = ^, then            //exponential operator of higher precedence
         push ^ into the stack
      else if ch = closing parenthesis ), then
         while stack is not empty and stack top ≠ (,
            do pop and add item from stack to postfix expression
         done

         pop ( also from the stack
      else
         while stack is not empty AND precedence of ch <= precedence of stack top element, do
            pop and add into postfix expression
         done

         push the newly coming character.
   done

   while the stack contains some remaining characters, do
      pop and add to the postfix expression
   done
   return postfix
End