postficcpp

Assignment 4/postfix.cpp

@@ -0,0 +1,58 @@
+#include<iostream>
+#include<stack>
+#include<math.h>
+using namespace std;
+// The function calculate_Postfix returns the final answer of the expression after calculation
+int calculate_Postfix(string  post_exp)
+{
+    stack <int> stack;
+    int lenth = post_exp.length();
+    // loop to iterate through the expression
+    for (int i = 0; i < lenth; i++)
+    {
+
+        if ( post_exp[i] >= '0' &&  post_exp[i] <= '9')
+        {
+            stack.push( post_exp[i] - '0');
+        }
+        // if the character is an operator we enter else block
+        else
+        {
+            // pop the top two elements from the stack and save them in two integers
+            int a = stack.top();
+            stack.pop();
+            int b = stack.top();
+            stack.pop();
+            //performing the operation on the operands
+            switch (post_exp[i])
+            {
+                case '+': // add
+                          stack.push(b + a);
+                          break;
+                case '-': // sub
+                          stack.push(b - a);
+                          break;
+                case '*': // mul
+                          stack.push(b * a);
+                          break;
+                case '/': // div
+                          stack.push(b / a);
+                          break;
+                case '^': // exp
+                          stack.push(pow(b,a));
+                          break;
+            }
+        }
+    }
+    //the calculated result
+    return stack.top();
+}
+// driver function
+int main()
+{
+    //we save the postfix expression to calculate in postfix_expression string
+    string postfix_expression = "70+65^2*5/-";
+    cout<<"The answer after calculating the postfix expression is : ";
+    cout<<calculate_Postfix(postfix_expression);
+    return 0;
+}