Create 3264_hcbbt.cpp

From http://blog.csdn.net/hcbbt/article/details/38581945

HDOJ/3264_hcbbt.cpp

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+/*
+*  Author:      illuz <iilluzen[at]gmail.com>
+*  Blog:        http://blog.csdn.net/hcbbt
+*  File:        3264.cpp
+*  Create Date: 2014-08-12 20:25:57
+*  Descripton:  Geometry, the insection of two round, binary
+*/
+
+#include <iostream>
+#include <cstdio>
+#include <cstring>
+#include <cmath>
+#include <algorithm>
+using namespace std;
+#define repf(i,a,b) for(int i=(a);i<=(b);i++)
+
+typedef long long ll;
+
+const int N = 21;
+const double PI = acos(-1.0);
+const double EPS = 1e-8;
+
+int t, n;
+
+struct Round {
+    double x, y;
+    double r;
+} r[N], ori;
+
+double dis(const Round &a, const Round &b) {
+    return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
+}
+
+double insection_of_rounds(Round &a, Round &b) {
+    double d = dis(a, b);
+    if (d >= a.r + b.r)
+        return 0;
+    if (d <= fabs(a.r - b.r)) {
+        double r = a.r < b.r ? a.r : b.r;
+        return PI * r * r;
+    }
+    double ang1 = acos((a.r * a.r + d * d - b.r * b.r) / 2. / a.r / d);
+    double ang2 = acos((b.r * b.r + d * d - a.r * a.r) / 2. / b.r / d);
+    double ret = ang1 * a.r * a.r + ang2 * b.r * b.r - d * a.r * sin(ang1);
+    return ret;
+}
+
+bool check(Round& ori) {
+    repf (i, 0, n - 1) {
+        if (insection_of_rounds(ori, r[i]) * 2 < PI * r[i].r * r[i].r)
+            return false;
+    }
+    return true;
+};
+
+double bin(double l, double r, Round& ori) {
+    double mid;
+    while (fabs(l - r) >= EPS) {
+        mid = (l + r) / 2;
+        ori.r = mid;
+        if (check(ori)) {
+            r = mid;
+        } else {
+            l = mid + EPS;
+        }
+    }
+    return mid;
+}
+
+int main() {
+    scanf("%d", &t);
+    while (t--) {
+        scanf("%d", &n);
+        repf (i, 0, n - 1) {
+            scanf("%lf%lf%lf", &r[i].x, &r[i].y, &r[i].r);
+        }
+        double ans = 1e10;
+        repf (i, 0, n - 1) {
+            ori.x = r[i].x;
+            ori.y = r[i].y;
+            double right = 0;
+            repf (j, 0, n - 1) {
+                right = max(right, dis(ori, r[j]) + r[j].r);
+            }
+            ans = min(ans, bin(0, right, ori));
+        }
+        printf("%.4f\n", ans);
+    }
+    return 0;
+}