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infixToPostfix.cpp
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infixToPostfix.cpp
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#include<iostream>
#include<math.h>
#include<stack>
using namespace std;
// Check Precedence
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<int>st;
string res;
for(int i=0;i<s.length();i++)
{
// For Operands
if((s[i]>='a' && s[i]<='z') || (s[i]>='A' && s[i]<='Z'))
{
// Print in the string
res+=s[i];
}
else if(s[i]=='(')
{
// if opening bracket than push it in the stack
st.push(s[i]);
}
else if(s[i]==')')
{
// if closing bracket then, while the stack is not empty and until it
// finds a opening bracket print every element in the string a keep poping each of them
// NOTE:- You dont have to print opening or closing bracket into string.
while(!st.empty() && st.top()!='(')
{
res+=st.top();
st.pop();
}
// if the stack is not empty then pop the opening bracket
if(!st.empty())
{
st.pop();
}
}
// For Operator
else
{
// if the precedence value of the operator of top is higher than the value to be inserted
// then print and pop the last operator and push the value that was meant to be inserted
while(!st.empty() && prec(st.top())>prec(s[i]))
{
res+=st.top();
st.pop();
}
st.push(s[i]);
}
}
// Print all the left elements in the string
while(!st.empty())
{
res+=st.top();
st.pop();
}
return res;
}
int main()
{
cout<<infixToPostfix("(a-b/c)*(a/k-l)")<<endl;
return 0;
}