数据结构中的计算表达式

#ifndef SQSTACK_H
#define SQSTACK_H

using namespace std;
template
class Stack
{
public:
virtual void clear()=0; //清空
virtual int leng()=0; //求长度
virtual bool full()=0; //判栈满
virtual bool empt()=0; //判空栈
virtual bool push (Telem& el)=0;
//将el推入栈中，操作成功返回true否则返回false
virtual Telem pop()=0; //若栈非空返回栈顶元素且删除栈顶元素，否则返回NULL
virtual Telem gettop()=0; //若栈非空返回栈顶元素，否则返回NULL
};

template
class SqStack :public Stack
{
private:
Telem *elem;
int top;
int maxlen;
public:
SqStack(int maxsz=100);
~SqStack(){delete[] elem;}
void clear(){top = -1;}
int leng(){ return top+1;}
bool push (Telem& el);
Telem pop( );
Telem gettop( );
bool full(){return top==maxlen-1;}
bool empt(){return top==-1;}
SqStack(Telem a[],int n,int maxsz);
friend ostream& operator<<(ostream& os,SqStack& sqs);
};

template
SqStack::SqStack(int maxsz):maxlen(maxsz)
{
top=-1;
elem=new Telem[maxlen];
}

template
SqStack::SqStack(Telem a[],int n,int maxsz):maxlen(maxsz)
{
elem=new Telem[maxlen];
for(int i=0;ielem[i]=a[i];
top=n-1;
}

template
bool SqStack::push(Telem& el)
{
if(full())
return false;
elem[++top]=el;
return true;
}

template
Telem SqStack::pop()
{
if(empt())
return NULL;
return elem[top--];
}

template
Telem SqStack::gettop()
{
if(empt())
return NULL;
return elem[top];
}

template
ostream& operator<<(ostream& os,SqStack& sqs)
{
for(int i=0;i<=sqs.top;i++)
os<return os;
}
#endif
#include
#include "sqstack.h"
using namespace std;

char r[7][7]={{'>','>','<','<','<','>','>'},
{'>','>','<','<','<','>','>'},
{'>','>','>','>','<','>','>'},
{'>','>','>','>','<','>','>'},
{'<','<','<','<','<','=',' '},
{'>','>','>','>',' ','>','>'},
{'<','<','<','<','<',' ','='}};

SqStack sopnd;
SqStack soprt;

char rela(char symb1,char symb2);
int oprt(int a,int b,char op);
bool comp(char st[],int& v);
void main()
{
char s[30]="#3*(7-2)#.";
//char s[30]="#7+5*(6/2)#.";
int num;
if(comp(s,num))
cout<}

char rela(char symb1,char symb2)
{
char ch[2];
int in[2];
ch[0]=symb1;
ch[1]=symb2;
for(int i=0;i<2;i++)
switch(ch[i])
{
case '+': in[i]=0;break;
case '-': in[i]=1;break;
case '*': in[i]=2;break;
case '/': in[i]=3;break;
case '(': in[i]=4;break;
case ')': in[i]=5;break;
case '#': in[i]=6;
}
return r[in[0]][in[1]];
}

int oprt(int a,int b,char op)
{
int re=0;
switch(op)
{
case '+': re=a+b;break;
case '-': re=a-b;break;
case '*': re=a*b;break;
case '/': re=a/b;
}
return re;
}

bool comp(char st[],int& v)
{
char ch,symb,op;
int a,b,i,n,r;
soprt.push(st[0]);
symb=st[1];
i=2;
while(symb!='.')
{
if((symb!='+') && (symb!='-') && (symb!='*')
&& (symb!='/') &&(symb!='(') && (symb!=')')
&& (symb!='#'))
{
n=symb-'0';
sopnd.push(n);
symb=st[i++];
}
else
{
ch=soprt.gettop();
switch(rela(ch,symb))
{
case '<':
soprt.push(symb);
symb=st[i++];
break;
case '=':
soprt.pop();
symb=st[i++];
break;
case '>':
op=soprt.pop();
b=sopnd.pop();
a=sopnd.pop();
r=oprt(a,b,op);
sopnd.push(r);
break;
}
}
}
if(soprt.empt())
{
v=sopnd.gettop();
return true;
}
else
return false;
}