1 /************************************************************** 2     Problem: 3680 3     User: rausen 4     Language: C++ 5     Result: Accepted 6     Time:300 ms 7     Memory:1040 kb 8 ****************************************************************/ 9  10 #include <cstdio>11 #include <cmath>12  13 using namespace std;14 typedef double lf;15 const int N = 10005;16 const lf eps = 1e-5;17  18 #define P point19 struct P {20     lf x, y;21     P() {}22     P(lf _x, lf _y) : x(_x), y(_y) {}23  24     inline P operator * (lf X) {25         return P(x * X, y * X);26     }27     inline P operator / (lf X) {28         return P(x / X, y / X);29     }30     inline P operator + (P a) {31         return P(x + a.x, y + a.y);32     }33      34     inline bool operator == (P a) {35         return fabs(x - a.x) < eps && fabs(y - a.y) < eps;36     }37     inline bool operator != (P a) {38         return fabs(x - a.x) >= eps || fabs(y - a.y) >= eps;39     }40 }p[N];41  42 int n;43 lf w[N];44  45 inline int read() {46     int x = 0, sgn = 1;47     char ch = getchar();48     while (ch < ‘0‘ || ‘9‘ < ch) {49         if (ch == ‘-‘) sgn = -1;50         ch = getchar();51     }52     while (‘0‘ <= ch && ch <= ‘9‘) {53         x = x * 10 + ch - ‘0‘;54         ch = getchar();55     }56     return sgn * x;57 }58  59 inline lf sqr(lf x) {60     return x * x;61 }62  63 inline lf dist(P a, P b) {  64     return sqrt(sqr(a.x - b.x) + sqr(a.y - b.y));65 }66  67 int main() {68     int i;69     lf W = 0;70     P p1 = P(0, 0), p2 = p1, p3;71     n = read();72     for (i = 1; i <= n; ++i) {73         p[i].x = read(), p[i].y = read(), w[i] = read();74         p1 = p1 + p[i] * w[i], W += w[i];75     }76     p1 = p1 / W;77     while (p1 != p2) {78         p2 = p3 = p1, p1 = P(0, 0);79         W = 0;80         for (i = 1; i <= n; ++i) {81             p1 = p1 + p[i] * (w[i] / dist(p3, p[i]));82             W += w[i] / dist(p3, p[i]);83         }84         p1 = p1 / W;    85     }86     printf("%.3lf %.3lf\n", p1.x, p1.y);87     return 0;88 }