C++ Program to reverse a string using do while

Program

#include <iostream>
#define MAX_SIZE 100 
using namespace std;
int main()
{
    char inputString[MAX_SIZE], reverseString[MAX_SIZE];
    int strIndex, revIndex, length;
    length = 0;
    cout << "Enter any string: ";
    cin >> inputString;
    while(inputString[length] != '\0')
    {
         length++;
    }   
    revIndex = 0;
    strIndex = length - 1;
    do {
        reverseString[revIndex] = inputString[strIndex];
        strIndex--;
        revIndex++;
    }while(strIndex >= 0);
    reverseString[revIndex] = '\0';
    cout << "Original string: " << inputString << endl;
    cout << "Reversed string: " << reverseString;
    return 0;
}

Output

$ g++ reverse-string-using-do-while.cpp 
$ ./a.out 
Enter any string: himalayas
Original string: himalayas
Reversed string: sayalamih