week-2019-10-20-answer.java

int magicFast(int[] array) {
    return magicFast(array, 0, array.length - 1);
}

int magicFast(int[] array, int start, int end) {
    if (end< start) {
        return -1;
    }
    int mid= (start+ end)/ 2;
    if (array[mid] == mid) {
        return mid;
    } else if (array[mid] > mid) {
        return magicFast(array, start, mid - 1);
    } else {
        return magicFast(array, mid+ 1, end);
    }
}