From 5a15a332ac6ebce7d6eada73bcf6e02cbc4eba17 Mon Sep 17 00:00:00 2001
From: Soham Dey <115808276+IamSohamDey@users.noreply.github.com>
Date: Sun, 16 Oct 2022 20:21:18 +0530
Subject: [PATCH] Create postfixtoprefix.c

---
 postfixtoprefix.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 postfixtoprefix.c

diff --git a/postfixtoprefix.c b/postfixtoprefix.c
new file mode 100644
index 0000000..e1c7b9b
--- /dev/null
+++ b/postfixtoprefix.c
@@ -0,0 +1,75 @@
+#include<stdio.h>
+#include<conio.h>
+#include<string.h>
+#include<stdlib.h>
+#define MAX 20
+char str[MAX], stack[MAX];
+int top = -1;
+void push(char c)
+{
+  stack[++top] = c;
+}
+char pop()
+{
+  return stack[top--];
+}
+int checkIfOperand(char ch)
+{
+  return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z');
+}
+int isOperator(char x) 
+{
+  switch (x) 
+  {
+  case '+':
+  case '-':
+  case '/':
+  case '*':
+  return 1;
+  }
+  return 0;
+}
+void postfixToprfix() 
+{
+  int n, i, j = 0;
+  char c[20];
+  char a, b, op;
+  printf("Postfix expression : \n");
+  scanf("%s", str);
+  n = strlen(str);
+  for (i = 0; i < MAX; i++)
+  stack[i] = '\0';
+  printf("Prefix expression : \n");
+  for (i = n - 1; i >= 0; i--)
+  {
+    if (isOperator(str[i]))
+    {
+      push(str[i]);
+    } else
+    {
+      c[j++] = str[i];
+      while ((top != -1) && (stack[top] == '#')) 
+      {
+        a = pop();
+        c[j++] = pop();
+      }
+      push('#');
+    }
+  }
+  c[j] = '\0';
+  i = 0;
+  j = strlen(c) - 1;
+  char d[20];
+  while (c[i] != '\0')
+  {
+    d[j--] = c[i++];
+  }
+  printf("%s\n", d);
+}
+int main() 
+{
+  postfixToprfix();
+  return 0;
+}
+
+