(哈夫曼树思想 )poj 3253 Fence Repair

<pre name="code" class="cpp">#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N=1000005;
int inf=0x3f3f3f3f;
ll mod=1e9+7;
long long a[20010],ans;
int main()
{
   int n;
   while(~scanf("%d",&n))
   {
       ans=0;
       for(int i=0;i<n;i++) scanf("%lld",&a[i]);
       while(n>1)
       {
           int sum;
           if(a[0]>a[1]) swap(a[0],a[1]);
           for(int i=2;i<n;i++)
           {
               if(a[0]>a[i])
               {
                   swap(a[0],a[i]);
                   swap(a[1],a[i]);
               }
               else if(a[1]>a[i])  swap(a[1],a[i]);
           }
           sum=a[0]+a[1];
           ans+=sum;
           a[0]=sum;
           a[1]=a[n-1];
           n--;
       }
       printf("%lld\n",ans);
   }
}

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<queue>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N=1000005;
int inf=0x3f3f3f3f;
ll mod=1e9+7;
long long a[20010],ans;
int main()
{
   int n;
   while(~scanf("%d",&n))
   {
       ans=0;
       for(int i=0;i<n;i++) scanf("%lld",&a[i]);
       priority_queue<ll, vector<ll>,greater<ll> >q;
       for(int i=0;i<n;i++) q.push(a[i]);
       while(q.size()>1)
       {
           ll a=q.top();q.pop();
           ll b=q.top();q.pop();
           ll sum=a+b;
           ans+=sum;
           q.push(sum);
       }
       printf("%lld\n",ans);
   }
}