added postfix to prefix conversion in cpp

Author: Mahakal0123

C++/Postfix_to_Prefix_Conversion.cpp

@@ -0,0 +1,44 @@
+#include <bits/stdc++.h>
+using namespace std;
+bool isOperator(char x)
+{
+	switch (x) {
+	case '+':
+	case '-':
+	case '/':
+	case '*':
+		return true;
+	}
+	return false;
+}
+string postToPre(string post_exp)
+{
+	stack<string> s;
+	int length = post_exp.size();
+	for (int i = 0; i < length; i++) {
+		if (isOperator(post_exp[i])) {
+			string op1 = s.top();
+			s.pop();
+			string op2 = s.top();
+			s.pop();
+			string temp = post_exp[i] + op2 + op1;
+			s.push(temp);
+		}
+		else {
+			s.push(string(1, post_exp[i]));
+		}
+	}
+
+	string ans = "";
+	while (!s.empty()) {
+		ans += s.top();
+		s.pop();
+	}
+	return ans;
+}
+int main()
+{
+	string post_exp = "ABC/-AK/L-*";
+	cout << "Prefix : " << postToPre(post_exp);
+	return 0;
+}