想使用sort函数结果报错了

#include<bits/stdc++.h>
using namespace std;
const int inf=1e5+10;
#define endl '\n'
int n;char a[25][25];
bool cmp(char a[],char b[])
{
    if(strcmp(a,b)>0)return 1;
    else return 0;
    return 0;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;i++)cin>>a[i];
    sort(a[1],a[1+n],cmp);
    for(int i=1;i<=n;i++)cout<<a[i];
    return 0;
}

[Error] invalid conversion from 'char' to 'char*' [-fpermissive]

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<string> a(n);
    for (int i = 0; i < n; i++)
        cin >> a[i];
    sort(a.begin(), a.end(), [](const auto &lhs, const auto &rhs)
         { return lhs > rhs; });
    for (int i = 0; i < n; i++)
        cout << a[i] << ' ';
    cout << endl;
    return 0;
}