C++ takes a string and outputs the characters in reverse order

Using the character array method:
The basic idea is to determine the end flag of a character '\0' and then print forward from that position.
Implementation code:

#include<iostream>
using namespace std;
int main(){
 char a[50];
 cout<<"please input a string:";
 cin>>a;
 int i=0,k=0;
 while(i<50){
        if(a[i]=='0'){
         k=i;
         break;
        }
        i++;
 }
       cout<<"reverse order: ";
        for(;k>=0;k--){
  cout<<a[k];
 }
 cout<<endl;
 return 0;

} 

With string method:
The basic idea is to determine the length of a character through the strlen() function and then output from the position of that length in the array.
Implementation code:

#include<iostream>
#include<string>
using namespace std;
int main(){
 char a[50];
 cout<<"please input a string:";
 cin>>a;
 int k=0;
 k=strlen(a);
 cout<<"Reverse order: ";
 for(;k>=0;k--){
  cout<<a[k];
 }
 cout<<endl;
 return 0;

}