P3382 【模板】三分法

R43941020

problem/P3382/P3382.cpp

@@ -0,0 +1,34 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const double eps = 1e-11;
+int n;
+double l, r, a[20], mid1, mid2;
+
+double f(double x) {
+    double s = 0;
+    for (int i = n; i >= 0; i--) {
+        s = s * x + a[i];
+    }
+    return s;
+}
+
+int main() {
+    cin >> n >> l >> r;
+    for (int i = n; i >= 0; i--) {
+        cin >> a[i];
+    }
+    while (r - l >= eps) {
+        mid1 = l + (r - l) / 3.0;
+        mid2 = r - (r - l) / 3.0;
+        if (f(mid1) > f(mid2)) {
+            r = mid2;
+        }
+        else {
+            l = mid1;
+        }
+    }
+    cout << fixed << setprecision(5) << l << endl;
+    return 0;
+}