52 lines
1.3 KiB
C++
52 lines
1.3 KiB
C++
#include<stdio.h>
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#include <memory.h>
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#include<stdlib.h>
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struct Exchange{
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int room;
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int javabean;
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};
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int cmp( const void *a , const void *b )
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{
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struct Exchange *c = (Exchange *)a;
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struct Exchange *d = (Exchange *)b;
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if (d->room*1.0/d->javabean > c->room*1.0/c->javabean)
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return 1;
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else if (d->room*1.0/d->javabean < c->room*1.0/c->javabean)
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return -1;
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else return 0;
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}
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double summation(Exchange* ex,int len,int javabeans)
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{
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double sum=0;
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qsort(ex,len,sizeof(Exchange),cmp);
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for(int i=0;i<len;i++)
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{
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if(javabeans-ex[i].javabean>0)
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{
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sum+=ex[i].room;
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javabeans-=ex[i].javabean;
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}
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else
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{
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sum+=javabeans*1.0/ex[i].javabean*ex[i].room;
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break;
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}
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}
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return sum;
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}
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int main()
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{
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int m,n;
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while(scanf("%d%d",&m,&n)!=EOF)
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{
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if(m==-1&&n==-1)
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break;
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Exchange* e=new Exchange[n];
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for(int i=0;i<n;i++)
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scanf("%d%d",&(e[i].room),&(e[i].javabean));
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double result=summation(e,n,m);
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printf("%.3lf\n",result);
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}
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return 0;
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}
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