Infix to postfix using Stack

As i said earlier, I am back with another post and this time around it's STACK time baby. So let's get started with Infix to postfix expression converter using Stacks. 

Mind you reader, this blog is for me to remember stuff i need to prepare before my placements so i'll be really up and about in my explanations. 

Anyway, let's get started!

#include<bits/stdc++.h>

using namespace std;

//function to print precedence of operators

int precedence(char c)

{

if(c=='^')

return 3;

else if(c=='*' || c=='/')

return 2;

else if(c=='+'|| c== '-')

return 1;

else

return -1;

}

//the function to convert infix to postfix

void intopost(string s)

{

stack<char> st; 

string result;

for(int i =0; i<s.length(); i++)

{

char c= s[i];

}

//if the scanned character is operand, add it to output string

if((c>='a' && c< ='z') || (c>='A' && c<='Z') || (c>='0' && c<='9'))

result+=c;

//if the scanned character is a '(' push it in stack

else if(c=='(')

st.push('(');

//if the scanned character is a ')' pop and output until a '(' is seen

else if(c==')')

while(!st.empty() && st.top() != '(')

char temp= st.top();

st.pop();

result+=temp;

st.pop();

//if an operator is scanned

else{

while(!st.empty() && precedence(s[i])<= precendence(st.top()))

char temp= st.top();

st.pop();

result+=temp;

st.push(c);

}

//pop remaining elements

while(!st.empty())

char temp= st.top();

st.pop();

result+=temp;

cout<<result<<endl;

}

int main()

{

string exp;

cin>>exp;

intopost(exp);

return 0;

}


And that's how you convert an Infix to Postfix using a Stack!

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