Create 2280-minimum-lines-to-represent-a-line-chart.js

Author: everthis

2280-minimum-lines-to-represent-a-line-chart.js

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+/**
+ * @param {number[][]} stockPrices
+ * @return {number}
+ */
+var minimumLines = function(stockPrices) {
+  let res = 1
+  const ma = stockPrices
+  const n = ma.length
+  if(n === 0 || n === 1) return 0
+  ma.sort((a, b) => a[0] - b[0])
+  const eps = 1e-30
+  let dx = ma[1][0] - ma[0][0], dy = ma[1][1] - ma[0][1]
+  for(let i = 2; i < n; i++) {
+    const cur = ma[i], pre = ma[i - 1]
+    const dxx = cur[0] - pre[0], dyy = cur[1] - pre[1]
+    if(BigInt(dxx) * BigInt(dy) !== BigInt(dx) * BigInt(dyy)) res++
+    dx = dxx
+    dy = dyy
+  }
+  
+  return res
+};
+
+function product(p1, p2, p3) {
+    // 首先根据坐标计算p1p2和p1p3的向量，然后再计算叉乘
+    // p1p2 向量表示为 (p2.x-p1.x,p2.y-p1.y)
+    // p1p3 向量表示为 (p3.x-p1.x,p3.y-p1.y)
+    return (p2.x-p1.x)*(p3.y-p1.y) - (p2.y-p1.y)*(p3.x-p1.x);
+}