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;
}