C++ 堆栈实现(不能正常工作)

Question

这是我在同一实验室中获得帮助的上一个线程。我的堆栈行为不正常，至少可以说，当我将一个项目添加到堆栈中以稍后打印时，它似乎没有正确添加。我总是打印出加号'(+)，不管我是否输入另一个操作数(*,/,+)。

我正在使用堆栈将用户输入的中缀表达式转换为后缀。除了最后打印出堆栈中的操作数外，它似乎工作正常。

#include <iostream>;  
#include <vector>  
using namespace std;  

class DishWell{  
public:  
    char ReturnFront(){  
        return Well.front();  
    }  
    void Push(char x){  
        Well.push_back(x);  
    }  
    void Pop(){  
        Well.pop_back();  
    }  
    bool IsEmpty(){  
        return Well.empty();  
    }  
private:  
    vector<char> Well;  
};  

bool Precidence(char Input, char Stack){  
    int InputPrecidence,StackPrecidence;  
    switch (Input){  
        case '*':  
            InputPrecidence = 4;  
            break;  
        case '/':  
            InputPrecidence = 4;  
            break;  
        case '+':  
            InputPrecidence = 3;  
            break;  
        case '-':  
            InputPrecidence = 3;  
            break;  
        case '(':  
            InputPrecidence = 2;  
            break;  
        default:  
            InputPrecidence = 0;  
    }  
switch (Stack){  
    case '*':  
        StackPrecidence = 4;  
        break;  
    case '/':  
        StackPrecidence = 4;  
        break;  
    case '+':  
        StackPrecidence = 3;  
        break;  
    case '-':  
        StackPrecidence = 3;  
        break;  
    case '(':  
        StackPrecidence = 2;  
        break;  
    default:  
        StackPrecidence = 0;  
}  
if(InputPrecidence>StackPrecidence) return true;  
else return false;  
}  

int main(int argc, char** argv) {  
    DishWell DishTray;  
    char Input;  
    bool InputFlag;  
    InputFlag = true;  
    cout<<"Enter Input, invalid input will terminate"<<endl;  
    while(InputFlag){  
        cout<<"Input: ";  
        cin>>Input;  
        cout<<endl;  
        if((((Input>='a'&&Input<='z')||(Input>='A'&&Input<='Z'))||Input>='0'&&Input<='9')))//If Digit or Number
            cout<<Input;  
        if((Input=='*'||Input=='/'||Input=='+'||Input=='-')){//if operand  
            if(DishTray.IsEmpty())  
                DishTray.Push(Input);  
            else if(Precidence(Input,DishTray.ReturnFront()))  
                DishTray.Push(Input);  
            else if(!Precidence(Input,DishTray.ReturnFront()))  
                cout<<"Output: "<<Input<<endl;  
        }  
        else if(!((((Input>='a'&&Input<='z')||(Input>='A'&&Input<='Z'))||(Input>='0'&&Input<='9')))||((Input=='*'||Input=='/'||Input=='+'||Input=='-')))//if not digit/numer or operand  
            InputFlag = false;  
    }  
    int counter = 0;  
    while(!DishTray.IsEmpty()){  
        counter++;  
        cout<<counter<<" Element "<<DishTray.ReturnFront()<<endl;  
        DishTray.Pop();  
    }  
    return 0;  

谢谢你，马凯尔贝尔

Answer 1

您的循环调用 front()，然后调用 pop_back()。这将始终返回 vector 中的第一个元素，直到弹出所有元素，因为您永远不会删除前面的元素。您的 ReturnFront() 方法可能应该是:

char ReturnBack(){  
    return Well.back();  
}  

最后是你的循环:

   while(!DishTray.IsEmpty()){  
        counter++;  
        cout<<counter<<" Element "<<DishTray.ReturnBack()<<endl;  // will return last element
        DishTray.Pop();  // actually pop the element printed
    }