HDU 4355 Party All the Time

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http://acm.hdu.edu.cn/showproblem.php?pid=4355

题意：坐标轴上有一些点，每个点有权值，找出一个位置，所有点到这个点的距离的三次方乘以权值的和最小。

用三分求解就可以了

#include <cstdio>#include <cstring>#include <cmath>#include <iostream>#include <algorithm>using namespace std;const double EPS = 1e-4;const int MAXN = 50000+100;int n, T;double a[MAXN];double b[MAXN];double maxlen(double t) {    double ans = 0;    for(int i = 0; i < n; ++i){ans += (a[i]-t)*(a[i]-t)*((fabs)(a[i]-t))*b[i];}    return ans;}int main() {    scanf("%d", &T);    for(int t = 1; t <= T; ++t) {        scanf("%d", &n);        for(int i = 0; i < n; ++i) {scanf("%lf %lf",&a[i],&b[i]);}        double l = -1e6 , r = 1e6;        while(l + EPS < r) {            double m1 = l + (r - l) / 3;            double m2 = r - (r - l) / 3;            if(maxlen(m1) < maxlen(m2)) r = m2;            else l = m1;        }printf("Case #%d: %.0lf\n", t, maxlen(l));    }return 0;}

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