How can I change the mathematicalexpression in C++?

I mean I want to change the user mathematical expression which is post fix to infix, the main point in this question is the algorithm of the program ,I want to start to analyse the post fix mathematical expression from the end of expression which start with mathematical operators .

 

 

Example: 

The user post fix expression :   k a b + c / t - *

the infix expression after changing :   k * (a + b) / c - t