23 lines
340 B
C++
23 lines
340 B
C++
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#include<iostream>
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using namespace std;
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bool ce[20001]={0};
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int main(){
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int n;
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int a[101],ans=0;
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cin>>n;
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for(int i=1;i<=n;i++){
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cin>>a[i];
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ce[a[i]]=1;
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}
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for(int i=1;i<=n-1;i++){
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for(int j=i+1;j<=n;j++){
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int now=a[i]+a[j];
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if(ce[now]==1){
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ans++;
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ce[now]=0;
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}
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}
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}
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cout<<ans;
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return 0;
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}
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