hdu 1202

点击打开链接#include <iostream>#include<cstdio>#include<algorithm>using namespace std;const double a[]={60,70,80,90,100};const double b[]={0,1,2,3,4};int main(){    int n;    while(scanf("%d",&n)==1)    {        double num,score;        double sum1=0,sum2=0;        for(int i=0;i<n;i++)        {            cin>>num>>score;            if(score==-1) {                    continue;            }            sum1+=num;            int p=upper_bound(a,a+5,score)-a;            sum2+=num*b[p];        }        if(sum1==0) printf("-1\n");        else printf("%.2f\n",sum2/sum1);    }    return 0;}