new file: P1883.cpp

P1883.cpp

@@ -0,0 +1,51 @@
+#include <bits/stdc++.h>
+#define int long long
+using namespace std;
+int t;
+int n;
+struct node
+{
+    int a, b, c;
+} a[20005];
+long double getmax(long double now)
+{
+    long double ans = INT_MIN;
+    for (int i = 1; i <= n; ++i)
+    {
+        ans = max(ans, a[i].a * now * now + a[i].b * now + a[i].c);
+    }
+    return ans;
+}
+signed main()
+{
+    scanf("%lld", &t);
+    while (t--)
+    {
+        scanf("%lld", &n);
+        for (int i = 1; i <= n; ++i)
+        {
+            scanf("%lld%lld%lld", &a[i].a, &a[i].b, &a[i].c);
+        }
+        long double l = 0, r = 1000;
+        for (int i = 1; i <= 1000 && l <= r; i++)
+        {
+            long double lmid = l + (r - l) / 3, rmid = l + 2 * (r - l) / 3;
+            long double lans = getmax(lmid), rans = getmax(rmid);
+            if (lans > rans)
+            {
+                l = lmid;
+                
+            }
+            else if (lans < rans)
+            {
+                r = rmid;
+            }
+            else
+            {
+                l = lmid, r = rmid;
+            }
+        }
+        printf("%.4Lf\n", (long double)(getmax(r)));
+    }
+    return 0;
+}