I would like to evaluate(not convert) infix expression in C++. If you posses algorithm or even implementation of such algorithm(may be not C++, any language... I will try to rewrite it to C++) share please.
Evaluation means give the value of expression. (2+2)*3 is 12
I am sorry, I forgot that I am talking about stack solution, cause I know the tree solution and It is not suitable this time : (.
By far the easiest way is to convert the infix expression to postfix notation using Dijkstra's Shunting-yard algorithm, and evaulate the result, which is, like, trivial. There are code samples of this all over the internet (take a look at Rosetta code or LiteratePrograms).
Alternatively, if you'd like to learn, and you'd like to enter the magical world of parsing and a bit of compiler theory, write a recursive descent parser. It's great fun.
Oh and, if you'd like something more robust, you could take a look at Pratt parsing, which is awesome. Here's a great article about it.
How do you got the expression? If you got it like
(3 + 4) - (1 * 2) + 1 =
http://cboard.cprogramming.com/cplusplus-programming/32682-inserting-infix-into-binary-tree.html
do a tree transversal of the tree like
Left Root Right
so it will be sth like this: 3 + 4 the result - the result of 1 * 2 the result + 1.If you got the expression like
34+12*-1+
you can simulate assembly like do a stack and if you get to an operator pop the last 2 elements in the stack and apply the operator: put 3 in stack, put 4 in stack, get op. + so pop the last 2 elements and use the operator. Now you got only 7 in stack. Now read until get an operator so in the stack you will have 7 1 2 after op. * in stack you got 7 2 after op. - you get only 5 in stack add 1 in stack: Stack 5 1, use the last operator + and get the final result 6.Ok, here is the code: