Added Postfix_Evaluationstack.cpp

Stack Algorithims/Postfix_Evaluationstack.cpp

@@ -0,0 +1,80 @@
+#include<iostream>
+#include <bits/stdc++.h>
+
+typedef long long int ll;
+
+using namespace std;
+
+#define SIZE 1000
+int top=-1;
+int stackk[SIZE];
+
+int pop()
+{
+ if(top==-1)
+ {printf("Stack UnderFlow\n");
+ return -12345678;}
+ else
+ return stackk[top--];
+}
+void push(int data)
+{
+ if(top==SIZE-1)
+ printf("Stack OverFlow!\n");
+ else 
+ stackk[++top]=data;
+}
+int peek()
+{
+ if(top==-1)
+ {printf("Stack UnderFlow!\n");
+ return -1;}
+ else
+ return stackk[top];
+}
+int main()
+{
+ string exp;
+ printf("Enter the Postfix expression--\n");
+ cin>>exp;
+ int l=exp.length(),k,op1,op2;
+ for(int i=0;i<l;i++)
+ { 
+ k=(int)exp[i];
+ if(k>=48&&k<=57)
+ push(k-48);
+ else
+ {
+ op1=pop();
+ op2=pop();
+ if(op1==-12345678||op2==-12345678)
+ {
+ printf("Not Enough Operands...Sorry!\n");
+ break;
+ }
+ char ch=exp[i];
+ switch(ch)
+ {
+ case '*': push(op2*op1);
+ break;
+ case '/': push(op2/op1);
+ break;
+ case '-': push(op2-op1);
+ break;
+ case '+': push(op2+op1);
+ break;
+ case '^': push(pow(op2,op1));
+ break;
+ }
+ }
+ }
+ if(op1!=-12345678&&op2!=-12345678)
+ {if(top==0){
+ printf("Output of %s is: %d\n\n",exp,peek());
+ }
+ else
+ printf("Too many Operands...Oops!\n");}
+ cout<<"Thank you!"<<endl;
+
+ return 0;
+}