2010上交:计算表达式

6/2+3+3*4

18

#include <iostream>
#include <stack>
using namespace std;
typedef int TYPE;
const int MAXN=1005;
char buf[MAXN];
bool isNum(char ch)
{
return '0'<=ch&&ch<='9';
}
int priority(char ch)
{
switch(ch)
{
case '+':return 1;
case '-':return 1;
case '*':return 2;
case '/':return 2;
}
}
TYPE cal(TYPE x,TYPE y,char ch)
{
switch(ch)
{
case '+':return x+y;
case '-':return x-y;
case '*':return x*y;
case '/':return x/y;
}
}
int main()
{
while(cin>>buf)
{
stack<TYPE> it;
stack<char> op;
TYPE e=0;
for(int i=0;buf[i];i++)
{
if(isNum(buf[i]))
{
e*=10;
e+=(buf[i]-'0');
}
else
{
it.push(e);
e=0;
if(op.empty())
{
op.push(buf[i]);
}
else
{
char now=buf[i];
char ctp=op.top();
int np=priority(now);
int tp=priority(ctp);
if(np>tp)
{
op.push(now);
}
else
{
do
{
char ch=op.top();op.pop();
TYPE y=it.top();it.pop();
TYPE x=it.top();it.pop();
TYPE z=cal(x,y,ch);
it.push(z);
}while(!op.empty()&&np<=priority(op.top()));
op.push(now);
}
}
}
}
it.push(e);
while(!op.empty())
{
char ch=op.top();op.pop();
TYPE y=it.top();it.pop();
TYPE x=it.top();it.pop();
TYPE z=cal(x,y,ch);
it.push(z);
}
TYPE res=it.top();
cout<<res<<endl;
}
return 0;
}

#include <cstdio>
using namespace std;
const int MAXN=1005;
int e[MAXN],top;
int main()
{
int x;
char op;
while(scanf("%d",&x)!=EOF)
{
top=0;
e[top++]=x;
while(scanf("%c",&op)!=EOF)
{
if(op=='\n')    break;
scanf("%d",&x);
switch(op)
{
case '+':e[top++]=x;break;
case '-':e[top++]=-x;break;
case '*':e[top-1]*=x;break;
case '/':e[top-1]/=x;break;
}
}
int res=0;
for(int i=0;i<top;i++)
{
res+=e[i];
}
printf("%d\n",res);
}
return 0;
}