String.h Library Function strrev (How to reverse a string without using strrev)

STRREV :
This funcion inputs an array(string) from user and outputs its reverse order.

Here is the Code: >>>

#include <iostream>
#include <stdio.h>
using namespace std;
void strrev(char []);
int strlen(char []);
int main()
{
    char arr[200];
    cout<<"Enter any statement to get its reverse. "<<endl;
    gets(arr);
    cout<<"After Being reversed : "<<endl;
    strrev(arr);
    return 0;
}
void strrev(char array[])
{
    int length,i;
    length = strlen(array)-1;
    char array1[length];
    for(i=0 ; array[i]!='\0' ; i++)
    {
        array1[length]=array[i];
        length--;
    }
    array1[length]='\0';
    cout<<array1;
}
int strlen(char array[])
{
    int sum=0;
    for(int i=0 ; array[i]!='\0' ; i++)
    {
        sum+=1;
    }
    return sum;
}