Given an array of integers `arr`, you are initially positioned at the first index of the array.

In one step you can jump from index `i` to index:

- `i + 1` where: `i + 1 < arr.length`.
- `i - 1` where: `i - 1 >= 0`.
- `j` where: `arr[i] == arr[j]` and `i != j`.

Return the minimum number of steps to reach the last index of the array.

Notice that you can not jump outside of the array at any time.

Example 1:

    Input: arr = [100,-23,-23,404,100,23,23,23,3,404]
    Output: 3
    Explanation: You need three jumps from index 0 --> 4 --> 3 --> 9. Note that index 9 is the last index of the array.

Example 2:

    Input: arr = [7]
    Output: 0
    Explanation: Start index is the last index. You do not need to jump.

Example 3:

    Input: arr = [7,6,9,6,9,6,9,7]
    Output: 1
    Explanation: You can jump directly from index 0 to index 7 which is last index of the array.

Constraints:

- `1 <= arr.length <= 5 * 104`
- `-108 <= arr[i] <= 108`