为什么输入正确符号后会显示“输入有误”

#include<iostream>
#include<stdio.h>
#include<stdlib.h>

using namespace std;

float add(float a, float b)
{
    return(a+b);
}
float minus(float a, float b)
{
    return(a-b);
}
float multi(float a, float b)
{
    return(a*b);
}
float div(float a, float b)
{
    return(a/b);
}
float calculate(float a, float b, char k)
{
    float s;
    switch(k)
    {
        case '+':
    s=add(a,b);
    break;
        case'-':
            s=minus(a,b);
            break;
        case '*':
            s=multi(a,b);
            break;
        case '/':
            s=div(a,b);
            break;
    }
    return(s);
}



int main()
{
    float a,b;
    char k;
    cout<<"             简易计算器"<<endl;
    cout<<"请输入运算符"<<endl;
    cin>>k;
    if(k!='*'||'-'||'+'||'/')
    {
        cout<<"输入有误"<<endl;
   
    if(k=='#')
    {
        //cout<<"计算结束"<<endl;
        
    }
    }

    cout<<"请输入运算数值"<<endl;
    cin>>a>>b;
    //cin.ignore (numeric_limits<std::streamsize >::max());
    //cin.ignore (numeric_limits<std::streamsize>::max());
    cout<<"结果为"<<calculate(a,b,k)<<endl;
   
    system("pause");
    return 0 ;
}