Glitched Rail Fence Cipher Encryption

Glitched Rail Fence Cipher Encryption

#include <iostream>
#include <string>

using namespace std;

string plaint;
int strleng;
int a=0;
int b=0;

void encrypt(){

    //stores entered text in string.
    cout << "ENTER TEXT (must be more than 4 chars):" << endl << ">";
    getline(cin, plaint);
    cout << endl;

    strleng = plaint.length();
    cout << "String Length: " << strleng << endl;

    if(strleng>4){

    //creates 2 char arrays that have a size of half the entered text.
    char mychars[strleng/2];
    char mychars2[strleng/2];

    //encrypts the text. Sets text of first array to the even positioned characters and text of second to odd positioned chars.
    for(int i=0;i<=strleng;i++){

        if(i % 2 == 0){ //If i is even.

            mychars[a] = plaint[i];
            a++;

        }else{

            mychars2[b] = plaint[i];
            b++;

        }
    }

    cout << "CIPHERTEXT: " << mychars << mychars2 << endl; //outputs the ciphertext, combines the arrays.

    }else{

        cout << "Invalid Input." << endl;

    }
}