43 lines
842 B
C++
43 lines
842 B
C++
#include <stdio.h>
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#include <string.h>
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#include <algorithm>
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using namespace std;
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struct node
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{
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int qian;
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int v;
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};
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bool cmp(node a,node b)
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{
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return a.qian>b.qian;
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}
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int main()
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{
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int rong,zhonglei;
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int i;
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node f[2000];
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while(scanf("%d",&rong)&&rong)
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{
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int jiazhi=0;
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scanf("%d",&zhonglei);
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for(i=1;i<=zhonglei;i++)
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scanf("%d%d",&f[i].qian,&f[i].v);
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sort(f+1,f+1+zhonglei,cmp);
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for(i=1;i<=zhonglei;i++)
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{
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if(rong-f[i].v>=0)
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{
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jiazhi+=f[i].v*f[i].qian;
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rong-=f[i].v;
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}
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else
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{
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jiazhi+=f[i].qian*rong;
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break;
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}
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}
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printf("%d\n",jiazhi);
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}
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return 0;
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}
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