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  • Can I Alter Postfix Notation to Prefix Notation with Small Tweak in C++

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    Preferred language using C++//

    Basically the expression below has been converted into a C++ postfix expression. Now i need to reckon the result.

    I used deque somehow, instead of stack, because i tried using stack and it didn't seem to work. but there's bug.

    8 9 + 1 7 - *


    Here's my code:

    #include <fstreaM>
    #include <string>
    #include <deque>

    using namespace std;

    int main(){
    ifstream inf("input.txt");
    ofstream outf("output.txt");

    string line; inf >> line;

    deque <int> stack;

    for(int i = 0; i < line.length(); i+=2){
    // char ch =;
    if( == '*'){
    stack.push_back(stack.pop_back() * stack.pop_back());
    }else if( == '+'){
    stack.push_back(stack.pop_back() + stack.pop_back());
    }else if( == '-'){
    stack.push_back(-stack.pop_back() + stack.pop_back());
    }else stack.push_back( '0');


    outf << stack.pop_back() << endl;

    return 0;


    With the code above can i alter with a small tweak and have it change into a Prefix Notation.

    I still prefer using the std::deque STL Library from C++.

 2 Answer(s)

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