C++中缀表达式转后缀表达式,如何转换括号呀! 改了一天啦

#include <iostream>
#include <string>

using namespace std;

string RPN;
char END='#',push='#';

int priority(char &ch){
    switch(ch){
        case '^':
            return 5;
        case '(':
            return 4;
        case ')':
            return 3;
        case '*':
        case '/':
            return 2;
        case '+':
        case '-':
            return 1;
        case '#':
            return -1;
        default:
            return 0;
    }
}

typedef struct SNode{
    struct SNode *top;
    char ch;
    struct SNode *next;
}*StackList;

typedef StackList operators;

void InitStack(operators &P){
    SNode *node=(SNode*)malloc(sizeof(SNode));
    node->top=NULL;
    node->ch='#';
    node->next=NULL;
    P->top=node;
}

void PushStack(operators &P,char &ch){
    cout<<"top:"<<P->top->ch<<"----Push:"<<ch<<endl;
    SNode *node=(SNode*)malloc(sizeof(SNode));
    node->top=NULL;
    node->ch=ch;
    node->next=P->top;
    P->top=node;
}

void PopStack(operators &P,char &ch){
    ch=P->top->ch;
    P->top=P->top->next;
    cout<<"Pop:"<<ch<<endl;
}

void PrintStack(operators &P){
    char ch='\0';
    while(P->top->ch!=END){
        PopStack(P,ch);
        if(ch!='('&&ch!=')')
            RPN+=ch;
        if(priority(P->top->ch)<priority(push)){
            push='#';
            break;
        }
    }
    if(P->top->ch=='('&&push!='('){
        PopStack(P,ch);
    }
    cout<<RPN<<endl;
}

void convert(operators &P,char &ch){
    cout<<"----------ing"<<ch<<endl;
    char temp=P->top->ch;
    if(priority(ch)){
        if(priority(temp)<priority(ch)){
            if(ch=='(')
                END='(';
            PushStack(P,ch);
            if(ch==')')
                PrintStack(P);
        }else{
            push=ch;
            PrintStack(P);
            PushStack(P,ch);
        }
    }else
        RPN+=ch;
}

int main(){
    operators P=(operators)malloc(sizeof(operators));
    P->top=NULL;
    P->ch=NULL;
    P->next=NULL;
    InitStack(P);
    string str;
    char ch='\0';
    cout<<"请输入中缀表达式："<<endl;
    cin>>str;
    for(short i=0;i<str.length();i++){
        ch=str[i];
        if(ch==' ')
            continue;
        convert(P,ch);
    }
    END='#';
    PrintStack(P);
    return 0;
}