Postfix Evaluation in C

Postfix_Evaluation/Postfix _Evaluation.c

@@ -0,0 +1,86 @@
+//Postfix Evaluation
+#include<stdio.h>
+#include<string.h>
+#include<ctype.h>
+
+struct stack
+{
+    char A[100];
+    int Top;
+};
+
+void push(struct stack *ps, char x)
+{
+    if(ps -> Top == 99)
+       printf("\nStack is Full\n");
+    else
+   {
+       ps -> Top = ps -> Top + 1;
+       ps -> A[ps -> Top] = x;
+   }
+}
+
+int evaluate(int op1, int op2, char c)
+{
+    if(c == '+')
+       return op1 + op2;
+    else if(c == '-')
+       return op1 - op2;
+    else if(c == '*')
+       return op1 * op2;
+    else if(c == '/')
+       return op1 / op2;
+}
+
+void print(struct stack s)
+{
+    int i;
+    for(i = 0 ; i <= s.Top ; i++)
+       printf("%d\t", s.A[i]);
+}
+
+int pop(struct stack *ps)
+{
+    int x;
+    if(ps -> Top == -1)
+       printf("Stack is empty!Element cant be deleted\n");
+    else
+    {
+       x = ps -> A[ps -> Top];
+       ps -> Top = ps -> Top - 1;
+       return x;
+    }
+}
+
+int main()
+{
+     int op1, op2, x, i;
+     char optr;
+     struct stack s;
+     s.Top = -1;
+     printf("Enter the postfix exp to be evaluated \n");
+     gets(s.A);
+     for(i = 0; i < strlen(s.A); i++)
+     {
+         if(isdigit(s.A[i]))
+            push(&s, s.A[i] - '0');
+         else if(s.A[i] == '+' || s.A[i] == '-' || s.A[i] == '*' || s.A[i] == '/')
+         {
+            op1 = pop(&s);
+            op2 = pop(&s);
+            optr = s.A[i];
+            x = evaluate(op2, op1, optr);
+            push(&s, x);
+         }
+      }
+
+      printf("The result is :  ");
+      print(s);
+      printf("\n");   
+}
+
+/*Input - Output Sample
+Enter the postfix exp to be evaluated 
+2 3 1 * + 9 -
+The result is :  -4
+*/