栈实现表达式求值

#include <bits/stdc++.h>
using namespace std;
const int N=1e3+10;
char s[N];
bool flag=0;
char p[N];
int ptt=0;
int num[N],ntt=0;
char Op[N];
int optt=0; 
map<char,int>F;
bool check(char c){
    return c=='('||c==')'||c>='0'&&c<='9';
}
int getres(char op,int a,int b){
    if(op=='+') return a+b;
    if(op=='-') return a-b;
    if(op=='*') return a*b;
    if(op=='/') return a/b;
}
int main(){
	F['(']=-1,F[')']=4;
    F['+']=0,F['-']=1,F['*']=2,F['/']=3;
    cin>>s;
    for(int i=0;s[i];i++){
    if(s[i]=='('||s[i]==')')
      if(!(s[i]==')'&&p[ptt]=='(')) p[++ptt]=s[i];
      else ptt--;
      if(!check(s[i])&&(i==0||!check(s[i-1]))) flag=1;
    }
     
    if(ptt){
        cout<<"ERROR:缺少括号";
        return 0;
    }
    if(flag){
        cout<<"ERROR:表达式缺操作数";
        return 0;
    }
    int k=0;
    for(int i=0;s[i];i++){
        if(s[i]>='0'&&s[i]<='9'){
            int sum=0;
            while(s[i]>='0'&&s[i]<='9') sum=sum*10+s[i]-'0',i++;
            i--;
            num[++ntt]=sum;
            cout<<sum;
        }
        else if(s[i]=='(') Op[++optt]=s[i];
        else if(s[i]==')'){
            while(Op[optt]!='('){
                char c=Op[optt--];
                int b=num[ntt--];
                int a=num[ntt--];
                num[++ntt]=getres(c,a,b);
                //cout<<"\n**"<<num[ntt]<<endl;
                if(c!='(')
                cout<<c;
            }
            optt--;
        }
        else{
            if(optt==0||F[Op[optt]]<F[s[i]]) Op[++optt]=s[i];
            else {
                while(optt>0&&F[Op[optt]]>=F[s[i]]){
                char c=Op[optt--];
                int b=num[ntt--];
                int a=num[ntt--];
                num[++ntt]=getres(c,a,b);
                //cout<<"\n::"<<num[ntt]<<endl;
                cout<<c;
                }
                Op[++optt]=s[i];
            }
        }
        /*cout<<"-----"<<endl;
        for(int j=1;j<=ntt;j++) cout<<num[j];
        cout<<endl;
        for(int j=1;j<=optt;j++) cout<<Op[j];
        cout<<endl;*/
    }
    while(optt>0){
    	 char c=Op[optt--];
                int b=num[ntt--];
                int a=num[ntt--];
                num[++ntt]=getres(c,a,b);
                cout<<c;
	}
	cout<<endl<<num[ntt];
}