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为什么我的输出是4啊?
答案是6
求大家指点
```c++
#include <bits/stdc++.h>
#define int long long
#define all(s) s.begin(),s.end()
using namespace std;
signed main()
{
int n;cin>>n;
vector<int>v1,v2;
int sum=0;
for(int i=1;i<=n;i++)
{
int x;cin>>x;x=abs(x);
if(i&1){sum+=x;v1.push_back(x);}
else {sum-=x;v2.push_back(x);}
}
sort( all(v1) );
sort( all(v2) ,greater<int>() );
// for(auto i:v1)cout<<i<<" ";cout<<endl;
// for(auto i:v2)cout<<i<<" ";cout<<endl;
// cout<<sum<<endl;
int i,j=0;
while( i < v1.size() && j < v2.size() )
{
if(v2[j]-v1[i]>0){sum+=2*(v2[j]-v1[i]); i++;j++;}
else break;
}
cout<<sum<<endl;
// 请在此输入您的代码
return 0;
}
```