求助,编译错误

#include<iostream>
#include<cstring>
using namespace std;
int main()
{
    char a[100];
    int n,i;
    cin>>a;
    n=strlen(a);
    if(a[0]=='-')
    cout<<"-";
    while(a[n-1]!="0")
    {
        n--;
    }
    for(i=n-1;i>=0;i--)
    {
        if(a[i]!="-")
        cout<<a[i]
    }
}
12    16    D:\c++语言测试\未命名1.cpp    [Error] ISO C++ forbids comparison between pointer and integer [-fpermissive]
18    12    D:\c++语言测试\未命名1.cpp    [Error] ISO C++ forbids comparison between pointer and integer [-fpermissive]
这是咋回事?(我目前没有提交)