不考虑优先级的加减乘除

#include <iostream>

using namespace std;

int main()
{
	char temp[256];
	cin>>temp;
	int rst=0;
	int ad=0;
	char smb='+';
	int i=-1;
	do
	{
		i++;
		if(temp[i]<=47||temp[i]=='\0')
		{
			switch (smb)
			{
			case '+':rst=rst+ad;break;
			case '-':rst=rst-ad;break;
			case '*':rst=rst*ad;break;
			case '/':if (ad==0) {cout<<rst<<endl;return 0;} else {rst=rst/ad;} ;break;
			default: break;
			}
			smb=temp[i];
			ad=0;
		}
		else
		{
			int ii=temp[i]-48;
			ad=ad*10+ii;
		}
	}while (temp[i]!='\0');
	cout<<rst<<endl;
	return 0;
}