From fc88ad6e570f3617d837db77a3075260429797de Mon Sep 17 00:00:00 2001
From: Shivansh Srivastava <42182955+Shivansh2407@users.noreply.github.com>
Date: Tue, 29 Jan 2019 16:08:01 +0530
Subject: [PATCH] Create InfixToPostfix

---
 InfixToPostfix | 142 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 InfixToPostfix

diff --git a/InfixToPostfix b/InfixToPostfix
new file mode 100644
index 0000000..d16204e
--- /dev/null
+++ b/InfixToPostfix
@@ -0,0 +1,142 @@
+// C++ program to convert an infix expression to a 
+// postfix expression using two precedence function 
+#include <bits/stdc++.h> 
+using namespace std; 
+
+
+// to check if the input character 
+// is an operator or a '(' 
+int isOperator(char input) 
+{ 
+	switch (input) { 
+	case '+': 
+		return 1; 
+	case '-': 
+		return 1; 
+	case '*': 
+		return 1; 
+	case '^': 
+		return 1; 
+	case '%': 
+		return 1; 
+	case '/': 
+		return 1; 
+	case '(': 
+		return 1; 
+	} 
+	return 0; 
+} 
+
+// to check if the input character is an operand 
+int isOperand(char input) 
+{ 
+	if (input >= 65 && input <= 90 
+		|| input >= 97 && input <= 122) 
+		return 1; 
+	return 0; 
+} 
+
+// function to return precedence value 
+// if operator is present in stack 
+int inPrec(char input) 
+{ 
+	switch (input) { 
+	case '+': 
+	case '-': 
+		return 2; 
+	case '*': 
+	case '%': 
+	case '/': 
+		return 4; 
+	case '^': 
+		return 5; 
+	case '(': 
+		return 0; 
+	} 
+} 
+
+// function to return precedence value 
+// if operator is present outside stack. 
+int outPrec(char input) 
+{ 
+	switch (input) { 
+	case '+': 
+	case '-': 
+		return 1; 
+	case '*': 
+	case '%': 
+	case '/': 
+		return 3; 
+	case '^': 
+		return 6; 
+	case '(': 
+		return 100; 
+	} 
+} 
+
+// function to convert infix to postfix 
+void inToPost(char* input) 
+{ 
+	stack<char> s; 
+
+	// while input is not NULL iterate 
+	int i = 0; 
+	while (input[i] != '\0') { 
+
+		// if character an operand 
+		if (isOperand(input[i])) { 
+			printf("%c", input[i]); 
+		} 
+
+		// if input is an operator, push 
+		else if (isOperator(input[i])) { 
+			if (s.empty() 
+				|| outPrec(input[i]) > inPrec(s.top())) 
+				s.push(input[i]); 
+			else { 
+				while (!s.empty() 
+					&& outPrec(input[i]) < inPrec(s.top())) { 
+					printf("%c", s.top()); 
+					s.pop(); 
+				} 
+				s.push(input[i]); 
+			} 
+		} 
+
+		// condition for opening bracket 
+		else if (input[i] == ')') { 
+			while (s.top() != '(') { 
+				printf("%c", s.top()); 
+				s.pop(); 
+
+				// if opening bracket not present 
+				if (s.empty()) { 
+					printf("Wrong input\n"); 
+					exit(1); 
+				} 
+			} 
+
+			// pop the opening bracket. 
+			s.pop(); 
+		} 
+		i++; 
+	} 
+
+	// pop the remaining operators 
+	while (!s.empty()) { 
+		if (s.top() == '(') { 
+			printf("\n Wrong input\n"); 
+			exit(1); 
+		} 
+		printf("%c", s.top()); 
+		s.pop(); 
+	} 
+} 
+
+// Driver code 
+int main() 
+{ 
+	char input[] = "a+b*c-(d/e+f^g^h)"; 
+	inToPost(input); 
+	return 0; 
+}