Add PolyRoots.cpp to repo

OmeletWithoutEgg · Mar 1, 2024 · 5854ba8 · 5854ba8
1 parent 29cd97e
commit 5854ba8
Showing 1 changed file with 16 additions and 0 deletions.
diff --git a/codes/Math/PolyRoots.cpp b/codes/Math/PolyRoots.cpp
@@ -0,0 +1,16 @@
+VD polyRoots(VD p, llf xmin, llf xmax) {
+  if (p.size() == 2) return {-p[0]/p[1]};
+  VD d = polyRoots(derivative(p), xmin, xmax), ret;
+  d.pb(xmin-1); d.pb(xmax+1); sort(all(d));
+  for (size_t i = 0; i + 1 < d.size(); i++) {
+    llf l = d[i], h = d[i+1]; bool s = eval(p, l) > 0;
+    if (s ^ (eval(p, h) > 0)) {
+      for (int _ = 0; _ < 60; _++) {
+        llf m = (l + h) / 2, f = eval(p, m);
+        ((f <= 0) ^ s ? l : h) = m;
+      }
+      ret.push_back((l + h) / 2);
+    }
+  }
+  return ret;
+}