2280 - Minimum Lines to Represent a Line Chart\.

Medium

You are given a 2D integer array stockPrices where <code>stockPricesi = day_i, price_i</code> indicates the price of the stock on day <code>day_i</code> is <code>price_i</code>. A line chart is created from the array by plotting the points on an XY plane with the X-axis representing the day and the Y-axis representing the price and connecting adjacent points. One such example is shown below:

Return the minimum number of lines needed to represent the line chart.

Example 1:

Input: stockPrices = \[\[1,7],2,6,3,5,4,4,5,4,6,3,7,2,8,1]

Output: 3

Explanation:

The diagram above represents the input, with the X-axis representing the day and Y-axis representing the price.

The following 3 lines can be drawn to represent the line chart:

• Line 1 (in red) from (1,7) to (4,4) passing through (1,7), (2,6), (3,5), and (4,4).

• Line 2 (in blue) from (4,4) to (5,4).

• Line 3 (in green) from (5,4) to (8,1) passing through (5,4), (6,3), (7,2), and (8,1).

It can be shown that it is not possible to represent the line chart using less than 3 lines.

Example 2:

Input: stockPrices = \[\[3,4],1,2,7,8,2,3]

Output: 1

Explanation: As shown in the diagram above, the line chart can be represented with a single line.

Constraints:

• <code>1 <= stockPrices.length <= 10⁵</code>

• stockPrices[i].length == 2

• <code>1 <= day_i, price_i<= 10⁹</code>

• All <code>day_i</code> are distinct.