Reversing an Equation

Given a mathematical equation using numbers/variables and +, -, *, /. Print the equation in reverse.

Examples:

Input : 20 - 3 + 5 * 2
Output : 2 * 5 + 3 - 20

Input : 25 + 3 - 2 * 11
Output : 11 * 2 - 3 + 25

Input : a + b * c - d / e
Output : e / d - c * b + a



Approach : The approach to this problem is simple. We iterate the string from left to right and as soon we strike a symbol we insert the number and the symbol in the beginning of the resultant string.

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to reverse an equation
#include <bits/stdc++.h>
using namespace std;
  
// Function to reverse order of words
string reverseEquation(string s)
{
    // Resultant string
    string result;
    int j = 0;
    for (int i = 0; i < s.length(); i++) {
          
        // A space marks the end of the word
        if (s[i] == '+' || s[i] == '-' || 
            s[i] == '/' || s[i] == '*') {
              
            // insert the word at the beginning
            // of the result string
            result.insert(result.begin(), 
                s.begin() + j, s.begin() + i);
            j = i + 1;
              
            // insert the symbol
            result.insert(result.begin(), s[i]);
        }
    }
      
    // insert the last word in the string 
    // to the result string
    result.insert(result.begin(), s.begin() + j, 
                                     s.end());
    return result;
}
  
// driver code
int main()
{
    string s = "a+b*c-d/e";
    cout << reverseEquation(s) << endl;
    return 0;
}

chevron_right


Output:

e/d-c*b+a

This article is contributed by Raghav Sharma. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



My Personal Notes arrow_drop_up

Improved By : Akanksha_Rai



Article Tags :
Practice Tags :


3


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.