算法竞赛入门经典:习题3-4 计算器

#include<iostream>
#include<string>
using namespace std;
int main(){
string s;
int num = 0;
int a[2] = {0};
int j = 0;
int oporate = 1;
int temp;
int size = 0;
int ans = 0;
cin>>s;
size = s.size();
for(int i=0;i<size;i++){
if(s[i]>='0'&&s[i]<='9'){
temp = s[i]-'0';
num=num*10+temp;
}
else if(s[i]=='+') oporate = 1,a[j] = num,num = 0,j++;
else if(s[i]=='-')  oporate = 2,a[j] = num,num = 0,j++;
else if(s[i]=='*') oporate = 3,a[j] = num,num = 0,j++;
else if(s[i]=='/') oporate =4,a[j] = num,num = 0,j++;
}

switch(oporate){
case 1: ans = a[0]+num;break;
case 2: ans = a[0]-num;break;
case 3: ans = a[0]*num;break;
case 4: ans = a[0]/num;break;
defualt:break;
}
cout<<ans;
return 0;
}