Expression Conversion using stack

Infix->Postfix || Infix->Prefix || Postfix->Infix || Postfix->Prefix || Prefix->Infix || Prefix->Postfix

This program is implemented using stack. Stack is FILO or LIFO structure this property of stack is used to convert the expression from one form to another

code:

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

int getWeight(char ch) {
switch (ch) {
case '^':return 3;
case '/':
case '*': return 2;
case '+':
case '-': return 1;
default : return 0;
}
}


void infix2postfix(char infix[], char postfix[], int size) {
stack<char> s;
int weight;
int i = 0;
int k = 0;
char ch;
   
while (i < size) 
{
ch = infix[i];
if (ch == '(') 
{
s.push(ch);
i++;
continue;
}
if (ch == ')') 
{
while (!s.empty() && s.top() != '(') 
{
postfix[k++] = s.top();
s.pop();
}
        
if (!s.empty()) 
{
s.pop();
}
i++;
continue;
}
weight = getWeight(ch);
if (weight == 0) {
         
postfix[k++] = ch;

}
else {
         
if (s.empty()) {
       
s.push(ch);
}
else {
            
while (!s.empty() && s.top() != '(' && weight <= getWeight(s.top())) 
{
postfix[k++] = s.top();
s.pop();
}
            
s.push(ch);
}
}

i++;
}
   
while (!s.empty()) {
postfix[k++] = s.top();
s.pop();
}
postfix[k] = 0; 
}

void infix2prefix(char infix[], char prefix[], int size) {
stack<char> s;
int weight;
int i = 0;
int k = 0;
char ch;
char infix0[size];
int m=0,n=size-1;
while(m<size)
{
if(infix[n]=='(')
infix0[m]=')';
else if(infix[n]==')')
infix0[m]='(';
else
infix0[m]=infix[n];
m++;
n--;
}
infix0[m]=0;
while (i < size) {
ch = infix0[i];
if (ch == '(') {
   
s.push(ch);
i++;
continue;
}
if (ch == ')') {
        
while (!s.empty() && s.top() != '(') {
prefix[k++] = s.top();
s.pop();
}
        
if (!s.empty()) {
s.pop();
}
i++;
continue;
}
weight = getWeight(ch);
if (weight == 0) {
       
prefix[k++] = ch;

}
else {
         
if (s.empty()) {
        
s.push(ch);
}
else {
            
while (!s.empty() && s.top() != '(' && weight < getWeight(s.top())) 
{
prefix[k++] = s.top();
s.pop();
}
            
s.push(ch);
}
}
i++;
}
  
while (!s.empty()) {
prefix[k++] = s.top();
s.pop();
}
prefix[k] = 0; 
}


string postfix2infix(char postfix1[],int size)
{
string infix1;
stack<string> s;
int k=0;
while(k<size)
{
char ch=postfix1[k];
int weight=getWeight(ch);
if(weight==0)
{
string e;
e=ch;
s.push(e);
}
else
{

string operand_2=s.top();
s.pop();
string operand_1=s.top();
s.pop();
s.push("("+operand_1+ch+operand_2+")");

}
k++;
}
infix1=s.top();
s.pop();
return infix1;
}


string postfix2prefix(char postfix1[],int size)
{
string prefix1;
stack<string> s;
int k=0;
while(k<size)
{
char ch=postfix1[k];
int weight=getWeight(ch);
if(weight==0)
{
string e;
e=ch;
s.push(e);
}
else
{

string operand_2=s.top();
s.pop();
string operand_1=s.top();
s.pop();
s.push(ch+operand_1+operand_2);

}
k++;
}
prefix1=s.top();
s.pop();
return prefix1;
}



string prefix2infix(char prefix1[],int size)
{
string infix1;
stack<string> s;
int k=size-1;
while(k>=0)
{
char ch=prefix1[k];
int weight=getWeight(ch);
if(weight==0)
{
string e;
e=ch;
s.push(e);
}
else
{

string operand_1=s.top();
s.pop();
string operand_2=s.top();
s.pop();
s.push("("+operand_1+ch+operand_2+")");

}
k--;
}
infix1=s.top();
s.pop();
return infix1;
}

string prefix2postfix(char prefix1[],int size)
{
string postfix1;
stack<string> s;
int k=size-1;
while(k>=0)
{
char ch=prefix1[k];
int weight=getWeight(ch);
if(weight==0)
{
string e;
e=ch;
s.push(e);
}
else
{

string operand_1=s.top();
s.pop();
string operand_2=s.top();
s.pop();
s.push(operand_1+operand_2+ch);

}
k--;
}
postfix1=s.top();
s.pop();
return postfix1;
}


// main
int main() 
{
char ch;
int c,size;
char infix[20],postfix[20],prefix[20],postfix1[20],prefix1[20];
string infix1,prefix2,postfix2;
do{
cout<<">>>>>>>>>>EXPRESSION CONVERSION<<<<<<<<<<<<\n";
cout<<"1]infix to other\n";
cout<<"2]postfix to other\n";
cout<<"3]prefix to other\n";
cout<<"4]Exit\n";
cout<<"\nENTER YOUR CHOISE :";
cin>>c;
if(c!=4){
switch(c)
{
case 1:
   
   cout<<"insert Infix Expression: ";
   cin>>infix;
   size = strlen(infix);
   infix2postfix(infix,postfix,size);
   infix2prefix(infix,prefix,size);
   cout<<"\nInfix Expression :: "<<infix;
   cout<<"\nPostfix Expression :: "<<postfix;
   cout<<"\nPrefix Expression :: ";
   
   for(int i=strlen(prefix)-1;i>=0;i--)
   {
   cout<<prefix[i];
   }
   cout<<endl<<endl;
   break;
case 2:
   
   cout<<"insert postfix Expression: ";
   cin>>postfix1;
   size = strlen(postfix1);
   infix1 = postfix2infix(postfix1,size);
   prefix2=postfix2prefix(postfix1,size);
   cout<<"\nPostfix Expression :: "<<postfix1;
   cout<<"\nInfix Expression :: "<<infix1;
   cout<<"\nPrefix Expression :: "<<prefix2;
   cout<<endl<<endl;
break;
case 3:
   
   cout<<"insert pretfix Expression: ";
   cin>>prefix1;
   size = strlen(prefix1);
   infix1 = prefix2infix(prefix1,size);
   postfix2=prefix2postfix(prefix1,size);
   cout<<"\nPrefix Expression :: "<<prefix1;
   cout<<"\nInfix Expression :: "<<infix1;
   cout<<"\nPostfix Expression :: "<<postfix2;
   cout<<endl<<endl;
break;

case 4:

   break;

}
cout<<"do you want to continue :";
cin>>ch;}
}while(ch=='y');
   
   return 0;
}