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evaluate_postfix.cpp
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evaluate_postfix.cpp
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// Copyright 2019 Souvik Biswas
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#include <iostream>
using namespace std;
// Defining the maximum size of the stack to be 10
#define MAX 10
float evaluatePostfix();
// Defining a class to store the member variables
// and member functions required
class Stack {
float stk[MAX];
public:
int top;
Stack(): top(-1) {}
void push(float );
float pop();
void display();
};
/*
ALGORITHM FOR PUSHING AN ELEMENT IN THE STACK:
1) IF TOP = MAX-1
WRITE Overflow
EXIT
2) TOP = TOP + 1
3) STACK[TOP] = VALUE
4) EXIT
*/
void Stack :: push(float value) {
// When the size of stack has reached maximum,
// we cannot insert any element
if(top == MAX-1) {
cout<<"The Stack is full !\n";
}
else {
// Incrementing top
top++;
// Store the value in the stack at top position
stk[top] = value;
}
}
/*
ALGORITHM FOR POPPING AN ELEMENT FROM THE STACK:
1) IF TOP = -1
WRITE Underflow
RETURN -1
EXIT
2) VALUE = STK[TOP]
3) TOP = TOP - 1
4) RETURN VALUE
5) EXIT
*/
float Stack :: pop() {
// When the size of stack is -1, the stack is empty
if(top == -1) {
return -1;
}
else {
// Store the top value
float value = stk[top];
// Decrement top
top --;
return value;
}
}
float evaluatePostfix() {
Stack s;
string exp;
int i=0;
float op1, op2, value;
cout<<"Enter the experssion: ";
getline(cin, exp);
while(exp[i] != '\0') {
if(isdigit(exp[i])) {
s.push((float)exp[i]-'0');
i++;
}
else {
op2 = s.pop();
op1 = s.pop();
switch(exp[i]) {
case '+': value = op1 + op2;
break;
case '-': value = op1 - op2;
break;
case '*': value = op1 * op2;
break;
case '/': value = op1 / op2;
break;
case '%': value = (int)op1 % (int)op2;
break;
}
s.push(value);
}
i++;
}
return s.pop();
}
int main() {
int option;
float result;
result = evaluatePostfix();
cout<<"The result is "<<result<<endl;
}