![\"\"](\"https://assets.leetcode.com/uploads/2022/03/30/ex0.png\")
You are given a 2D integer array stockPrices where stockPrices[i] = [dayi, pricei] indicates the price of the stock on day dayi is pricei. 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:
![\"\"](\"https://assets.leetcode.com/uploads/2022/03/30/1920px-pushkin_population_historysvg.png\")
\nReturn the minimum number of lines needed to represent the line chart.
\n\n\n
Example 1:
\n\n\nInput: stockPrices = [[1,7],[2,6],[3,5],[4,4],[5,4],[6,3],[7,2],[8,1]]\nOutput: 3\nExplanation:\nThe diagram above represents the input, with the X-axis representing the day and Y-axis representing the price.\nThe following 3 lines can be drawn to represent the line chart:\n- Line 1 (in red) from (1,7) to (4,4) passing through (1,7), (2,6), (3,5), and (4,4).\n- Line 2 (in blue) from (4,4) to (5,4).\n- Line 3 (in green) from (5,4) to (8,1) passing through (5,4), (6,3), (7,2), and (8,1).\nIt can be shown that it is not possible to represent the line chart using less than 3 lines.\n\n\n
Example 2:
\n![\"\"](\"https://assets.leetcode.com/uploads/2022/03/30/ex1.png\")
\n\nInput: stockPrices = [[3,4],[1,2],[7,8],[2,3]]\nOutput: 1\nExplanation:\nAs shown in the diagram above, the line chart can be represented with a single line.\n\n\n
\n
Constraints:
\n\n1 <= stockPrices.length <= 105stockPrices[i].length == 21 <= dayi, pricei <= 109dayi are distinct.给你一个二维整数数组 stockPrices ，其中 stockPrices[i] = [dayi, pricei] 表示股票在 dayi 的价格为 pricei 。折线图 是一个二维平面上的若干个点组成的图，横坐标表示日期，纵坐标表示价格，折线图由相邻的点连接而成。比方说下图是一个例子：
\n请你返回要表示一个折线图所需要的 最少线段数 。
\n\n\n\n
示例 1：
\n\n
输入：stockPrices = [[1,7],[2,6],[3,5],[4,4],[5,4],[6,3],[7,2],[8,1]]\n输出：3\n解释：\n上图为输入对应的图，横坐标表示日期，纵坐标表示价格。\n以下 3 个线段可以表示折线图：\n- 线段 1 （红色）从 (1,7) 到 (4,4) ，经过 (1,7) ，(2,6) ，(3,5) 和 (4,4) 。\n- 线段 2 （蓝色）从 (4,4) 到 (5,4) 。\n- 线段 3 （绿色）从 (5,4) 到 (8,1) ，经过 (5,4) ，(6,3) ，(7,2) 和 (8,1) 。\n可以证明，无法用少于 3 条线段表示这个折线图。\n\n\n
示例 2：
\n\n
输入：stockPrices = [[3,4],[1,2],[7,8],[2,3]]\n输出：1\n解释：\n如上图所示，折线图可以用一条线段表示。\n\n\n
\n\n
提示：
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