From a566c2ace9af491ecb2f5ac4d429ac50a8d53e1a Mon Sep 17 00:00:00 2001
From: anand-aman <54910807+anand-aman@users.noreply.github.com>
Date: Thu, 19 Dec 2019 01:55:28 +0530
Subject: [PATCH] Issue #159

Infix to Postfix Expression using Stack in C language #159
---
 InfixToPostfix.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 InfixToPostfix.c

diff --git a/InfixToPostfix.c b/InfixToPostfix.c
new file mode 100644
index 0000000..79adf04
--- /dev/null
+++ b/InfixToPostfix.c
@@ -0,0 +1,73 @@
+#include<stdio.h>
+#include<stdlib.h>
+#include<ctype.h>
+
+char stack[50];
+int top=-1;
+
+void push(char ch)
+{
+	stack[++top]=ch;
+}
+
+int pop(){
+	return(stack[top--]);
+}
+
+int prior(char ch)
+{
+    int p;
+
+	if(ch=='#' || ch=='(')
+		p=1;
+	if(ch=='+' || ch=='-')
+		p=2;
+	if(ch=='*' || ch=='/')
+		p=3;
+	if(ch=='$' || ch=='^')
+		p=4;
+
+	return p;
+}
+
+int main()
+{
+	char infix[100], postfix[100];
+	int i=0,j=0;
+
+	printf("Enter infix expression: ");
+	scanf("%s",infix);
+
+	push('#');
+
+	for (int i = 0; i < strlen(infix); i++)
+	{
+		if(isalnum(infix[i]))
+			postfix[j++]=infix[i];
+
+		else if(infix[i] == '(')
+			push(infix[i]);
+
+		else if(infix[i]==')')
+		{
+			while(stack[top]!='(')
+				postfix[j++] = pop();
+			pop();
+		}
+
+		else
+		{
+			while(prior(stack[top])>=prior(infix[i]))
+				postfix[j++]=pop();
+			push(infix[i]);
+		}
+	}
+
+	while(stack[top]!='#')
+		postfix[j++]=pop();
+	postfix[j]='\0';
+
+	printf("Postfix expression: ");
+	printf("%s\n",postfix);
+	return 0;
+}