Merge pull request #174 from adiXcodr/master

A calculator that converts Infix to Prefix, Postfix and also calculat…

Author: bhrigukansra

Data Structures/Stack/C++/infixCalculator.cpp

@@ -0,0 +1,134 @@
+
+#include <bits/stdc++.h>
+#include<string>
+#include<stack>
+using namespace std;
+
+
+    string removeSpaces(string s)
+    {
+        s.erase(remove(s.begin(), s.end(), ' '), s.end());
+        return s;
+    }
+
+    bool isOperator(char c)
+    {
+       return (!isalpha(c) && !isdigit(c));
+    }
+
+    int getPriority(char C)
+    {
+      if (C == '-' || C == '+')
+        return 1;
+      else if (C == '*' || C == '/')
+        return 2;
+      else if (C == '^')
+        return 3;
+      return 0;
+    }
+
+    string infixToPostfix(string infix)
+    {
+      infix = '(' + infix + ')';
+      int l = infix.size();
+      stack<char> char_stack;
+      string output;
+
+      for (int i = 0; i < l; i++) {
+        if (isalpha(infix[i]) || isdigit(infix[i]))
+          output += infix[i];
+        else if (infix[i] == '(')
+          char_stack.push('(');
+        else if (infix[i] == ')') {
+          while (char_stack.top() != '(') {
+            output += char_stack.top();
+            char_stack.pop();
+          }
+          char_stack.pop();
+        }
+        else {
+
+          if (isOperator(char_stack.top())) {
+            while (getPriority(infix[i])
+            <= getPriority(char_stack.top())) {
+              output += char_stack.top();
+              char_stack.pop();
+            }
+            char_stack.push(infix[i]);
+          }
+        }
+      }
+      return output;
+    }
+
+    string infixToPrefix(string infix)
+    {
+      int l = infix.size();
+      reverse(infix.begin(), infix.end());
+      for (int i = 0; i < l; i++) {
+        if (infix[i] == '(') {
+          infix[i] = ')';
+          i++;
+        }
+        else if (infix[i] == ')') {
+          infix[i] = '(';
+          i++;
+        }
+      }
+
+      string prefix = infixToPostfix(infix);
+      reverse(prefix.begin(), prefix.end());
+      return prefix;
+    }
+
+
+int postfixEval(string exp) {
+   stack <int> x;
+   for (int i = 0; exp[i]; ++i)
+    {
+        if (isdigit(exp[i]))
+            x.push(exp[i] - '0');
+
+        else
+        {
+            int val1 = x.top();
+            x.pop();
+            int val2 = x.top();
+            x.pop();
+            switch (exp[i])
+            {
+            case '+': x.push( val2 + val1); break;
+            case '-': x.push( val2 - val1); break;
+            case '*': x.push(val2 * val1); break;
+            case '/': x.push( val2/val1); break;
+            }
+        }
+    }
+    return x.top();
+}
+
+
+
+    int main(int argc, char *argv[])
+    {
+      int value;
+      string s;
+      for (int i=1;i<argc;i++){
+        s.append(argv[i]).append(" ");
+      }
+      if(argc=1){
+        cout<<"No Arguments Passed\nEnter expression here\n";
+        getline(cin,s);
+      }
+      if(s.size()>=1){
+      s=removeSpaces(s);
+      cout<<"Postfix : "<<infixToPostfix(s)<<endl;
+      cout<<"Prefix : "<<infixToPrefix(s)<<endl;
+      s=infixToPostfix(s);
+      value=postfixEval(s);
+      cout<<"Value : "<<value<<endl;
+      }
+      else
+      cout<<"Value : 0"<<endl;
+      return 0;
+    }