# Changing Directions

Given a list of integers `nums`

, return the number of times that the list changes from positive-to-negative or negative-to-positive slope.

**Constraints**

`n ≤ 100,000`

where`n`

is the length of`nums`

https://binarysearch.com/problems/Changing-Directions

## Examples

### Example 1

**Input**

- nums =
`[1, 3, 9, 7, 5, 10, 12]`

**Output**

- answer =
`2`

**Explanation**

Change of direction happens at `9`

(positive-to-negative slope), and then at `5`

(negative-to-positive slope).

### Example 2

**Input**

- nums =
`[1, 2, 3, 3, 2, 1]`

**Output**

- answer =
`0`

**Explanation**

The slope is `0`

between `[3, 3]`

. So there are no positive-to-negative or negative-to-positive changes in slope since 0 is neither positive nor negative.

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