leetcode周赛6076. 表示一个折线图的最少线段数

class Solution {
    public int minimumLines(int[][] stockPrices) {
    
        Arrays.sort(stockPrices,(o1,o2)->o1[0]-o2[0]);

        int n = stockPrices.length;
        if (n == 1) return 0;
        int ans = 1;

        for (int i = 0; i < n-2; i++) {
            int k1 = stockPrices[i+1][0] - stockPrices[i][0];
            int k2 = stockPrices[i+1][1] - stockPrices[i][1];

            int k3 = stockPrices[i+2][0] - stockPrices[i+1][0];
            int k4 = stockPrices[i+2][1] - stockPrices[i+1][1];

            if (k2*k3 != k1 * k4) ans++;
        }

        return ans;
    }
}