Double a (Solution without making another string)

#include <iostream>
#include <string.h>
using namespace std;

char double_a(char string[])
{
    for (int i = 0; i < strlen(string); i++)
    {
        if (string[i] == 'a')
        {
            for (int j = strlen(string); j > i + 1; j--)
            {
                string[j] = string[j - 1];
            }

            string[i + 1] = 'a';
        }
    }

	//Needs to return an actual string, but I'm too lazy to finish it off
}

int main()
{
    char base[20] = "Yoona eats flowers";

    double_a(base);
    cout << base;
}