topcode SRM 577 DIV1 EllysRoomAssignmentsDiv1

注意分情况求期望

（1）只分配一个房间时，也就是人数少于20，对应测试用例1

（2）刚好完全分配时，对应测试用例3

（3）不能完全分配，最后还剩余的竞技者的数量小于房间数，随机分配

　　　a)  当elly刚好在最后剩余的里面，也就是elly排最后几名，对应测试用例4

　　   b)  当elly不在最后剩余的里面 ，对应测试用例0和2

#include <iostream>
#include <numeric>
#include <vector>
#include <string>
#include <algorithm>
#include <sstream>
#include <cmath>

using namespace std;

class EllysRoomAssignmentsDiv1{
public:
    double getAverage(vector <string> ratings){
        string split="";
        string all = accumulate(ratings.begin(),ratings.end(),split);
        stringstream sst(all);
        vector<int> score;
        int tmp;
        while(sst >> tmp) score.push_back(tmp);
        int score_elly = score[0];
        sort(score.begin(),score.end(),greater<int>());
        int cnt_elly = 0;
        for(int i = 0 ; i < score.size(); i ++  ){
            if( score[i] == score_elly) {
                cnt_elly = i;break;
            }
        }
        int R = score.size()%20 ? score.size()/20+1 : score.size()/20;
        double value = 0;
        for(int i = 0 ; i < score.size()/R; i ++ ){
            if( i == cnt_elly/R ) continue;
            double sum = 0;
            for(int j = 0; j < R; j ++ ) sum +=score[R*i+j];
            value +=sum/R;
        }
        if(R == 1){
            return (value+score_elly)/score.size();
        }
       else if(score.size()%R){
                double otherValue = 0;
                int otherStart = score.size()/R*R;
            if(cnt_elly < otherStart){
                for(int i =otherStart; i < score.size(); i ++ )
                    otherValue += score[i];
                otherValue /=(score.size()-otherStart);
                  return (value+otherValue+score_elly)/(score.size()/R+1)/R*(score.size()-otherStart) + (value+score_elly)/(score.size()/R)/R*(R-score.size()+otherStart);
              }
              else{
                  return (value+score_elly)/(score.size()/R+1);
              }
        }
        else{
            return (value+score_elly)/(score.size()/R);
        }
    }
};