C + + 이 진 트 리 응용: 계산 산술 표현 식

#include<iostream>
using namespace std;
class calc
{
	enum Type{DATA,ADD,SUB,MULTI,DIV,OPAREN,CPAREN,EOL};
	struct node
	{
		Type type;
		int data;
		node *lchild,*rchild;
		node(Type t,int d=0,node*lc=NULL,node *rc=NULL)
		{
			type=t;
			data=d;
			lchild=lc;
			rchild=rc;
		}
	};
	node *root;
	node *create(char *&s);
	Type getToken(char *&s,int &value);
	int result (node *t);
public:
	calc(char *s){root=create(s);}
	int result()
	{
		if(root==NULL)return 0;
		return result(root);
	}
};


calc::node *calc::create(char *&s)
{//((2+3*2)-(12-6))/2=1
	node *p,*root=NULL;
	Type returnType=DATA;Type flag=DATA;
	int value;
	while(*s)
	{
		flag=returnType;
		returnType=getToken(s,value);
		switch(returnType)
		{
		case DATA:
		case OPAREN:
			if(returnType==DATA)
				p=new node(DATA,value);
			else p=create(s);
			if(root==NULL)root=p;
			else if(root->rchild==NULL)
				root->rchild=p;
			else root->rchild->rchild=p;break;
		case CPAREN:
		case EOL:return root;
		case ADD:
		case SUB:
			root=new node(returnType,0,root);break;
		case MULTI:
		case DIV:
			if(root->type==DATA||root->type==MULTI||root->type==DIV||flag==OPAREN)
				root=new node(returnType,0,root);
			else root->rchild=new node(returnType,0,root->rchild);
		}
	}
	return root;
}
calc::Type calc::getToken(char *&s,int &data)
{
	char type;
	while(*s==' ')++s;
	if(*s>='0'&&*s<='9')
	{
		data=0;
		while(*s>='0'&&*s<='9')
		{
			data=data*10+*s-'0';
			++s;
		}
		return DATA;
	}
	if(*s=='\0')return EOL;
	type=*s;
	++s;
	switch(type)
	{
	case '+':return ADD;
	case '-':return SUB;
	case '*':return MULTI;
	case '/':return DIV;
	case '(':return OPAREN;
	case ')':return CPAREN;
	default:return EOL;
	}
}

int calc::result(node*t)
{
	int num1,num2;
	if(t->type==DATA)return t->data;
	num1=result(t->lchild);
	num2=result(t->rchild);
	switch(t->type)
	{
	case ADD:t->data=num1+num2;break;
	case SUB:t->data=num1-num2;break;
	case MULTI:t->data=num1*num2;break;
	case DIV:t->data=num1/num2;break;
	}
	return t->data;
}

int main()
{
	char equation[256];
	cin>>equation;
	//calc exp("3*(2+(6/2))");
	calc exp(equation);
	cout<<exp.result()<<endl;
	return 0;
}