Notes

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

struct nodeType
{
int info;
nodeType *next;
};

class linkedStackType
{
public:
linkedStackType();
void push(int);
void pop();
int top();

private:
nodeType *stackTop;
};

linkedStackType::linkedStackType()
{
stackTop = NULL;
}


void linkedStackType::push(int item)
{
nodeType *newNode = new nodeType;
newNode->info = item;

newNode->next = stackTop;
stackTop = newNode;
}

int linkedStackType::top()
{
assert(stackTop == NULL);

return stackTop->info;
}

void linkedStackType::pop()
{
if(stackTop == NULL)
cout<<"Empty stack" << endl;
else
{
nodeType *current = stackTop;
stackTop = stackTop->next;
delete current;
}
}






bool process (char ch)
{
if (ch=='+' || ch=='-' || ch=='*' || ch=='/')
return true;
return false;
}


int implementation(int X1, int X2, char proc)
{
int Temp;
switch(proc){
case '+':
Temp = X2 + X1;
break;
case '-':
Temp = X2 - X1;
break;
case '*':
Temp = X2 * X1;
break;
case '/':
Temp = X2 / X1;
break;
}
return Temp;
}















int main()
{
linkedStackType s1;

for(int i = 1; i <= 20; i++)
s1.push(i);






char exp[1000], buffer[15];
int i,op1, op2, len, j, x;
linkedStackType s2;
cout<<"Please Enter a postfix Exp : ";
cin>>exp;
len = strlen(exp);
j = 0;
for(i=0; i<len;i++){

if(exp[i]>='0' && exp[i]<='9'){
buffer[j++] = exp[i];
}
else if(exp[i]==' '){
if(j>0){
buffer[j] = '';
x = atoi(buffer);
s2.push(x);
j = 0;
}
}

else if(process(exp[i])){
op1 = s2.top();
s2.pop();
op2 = s2.top();
s2.pop();
s2.push(implementation(op1, op2, exp[i]));
}
}

cout << s1.top() << endl;

return 0;
}