求高手大大指点迷津！！！！if语句的问题，里面嵌switch语句

#include "iostream.h"
#include "stdlib.h"
int main()
{
    float a,b,c,temp;
    char oper1,oper2;
    cout <<"请输入一个表达式（eg.1+2*3）：" <<endl;
    cin >>a >>oper1 >>b >>oper2 >>c;
    if ((oper1!='*' &&oper1!='/') && (oper2=='*'||oper2=='/'))
    {
        switch (oper2)
        {
        case '*':
            {
                temp=b*c;
                break;
            }
        case '/':
            {
                if (c!=0) temp=b/c;
                else
                {
                    cout <<"出错啦！"<<endl;
                    exit(1);
                }
                break;
            }
        default:
            cout <<"出错啦！"<<endl;
            exit(1);
        }
        switch (oper1)
            {
            case '+':
                {
                    temp=a+temp;
                    break;
                }
            case '-':
                {
                    temp=a-temp;
                    break;
                }
            default:
                cout <<"出错啦！"<<endl;
                exit(1);
            }
    }
    else
    {
            switch (oper1)
            {
            case '+':
                {
                    temp=a+b;
                    break;
                }
            case '-':
                {
                    temp=a-b;
                    break;
                }
            case '*':
                {
                    temp=a*b;
                    break;
                }
            case '/':
                {
                    if (b!=0) temp=a/b;
                    else
                    {
                        cout <<"出错啦！"<<endl;
                        exit(1);
                    }
                    break;
                }
            default:
                cout <<"出错啦！"<<endl;
                exit(1);
            }
            switch (oper2)
            {
            case '+':
                {
                    temp=temp+c;
                    break;
                }
            case '-':
                {
                    temp=temp-c;
                    break;
                }
            case '*':
                {
                    temp=temp*c;
                    break;
                }
            case '/':
                {
                    if (c!=0) temp=temp/c;
                    else
                    {
                        cout <<"出错啦！"<<endl;
                        exit(1);
                    }
                    break;
                }
            default:
                cout <<"出错啦！"<<endl;
                exit(1);
            }
    }
    cout <<a <<oper1 <<b <<oper2 <<c <<'=' <<temp <<endl;
return 0;
}

注意红色部分，为什么换成if ((oper2=='*' || oper2=='/') && (oper1!='*' && oper1!='/'))后，
运算a*b*c,或a/b/c时，结果是"出错了!"呢？
if ((oper2=='*' || oper2=='/') && (oper1!='*' && oper1!='/'))
 if ((oper1!='*' &&oper1!='/') && (oper2=='*'||oper2=='/'))
这两个条件不是一样的么？
求高手大大指点迷津！！！！