#include<iostream>
#include<stdlib.h>
#define N 30000
using namespace std;
int a[N+1],o=0;
typedef struct 
{
	int weight;
	int parent,lchild,rchild;
}htnode;
typedef struct
{
	int weight;
}htcode;
void huffmanselect(htnode ht[],int k,int *s1,int *s2)//挑选所给结点两个最小的.
{
	int i;
	for(i=1;i<=k && ht[i].parent!=0;i++)
	{
		;;
	}
	*s1=i;
    for(i=1;i<=k;i++)
	{
		if(ht[i].parent==0 && ht[i].weight<ht[*s1].weight)
			*s1=i;
	}
	for(i=1;i<=k;i++)
	{
		if(ht[i].parent==0 && i!=*s1)
			break;
	}
	*s2=i;
	for(i=1;i<=k;i++)
	{
		if(ht[i].parent==0 && ht[i].weight<ht[*s2].weight && i!=*s1)
			*s2=i;
	}
}
void huffmantree(htnode ht[],htcode hc[],int n)//构建哈夫曼树
{
	int i,m,s1,s2;
	m=2*n-1;
	for(i=1;i<=m;i++)
	{
		if(i<=n)
			ht[i].weight=hc[i].weight;
		else
			ht[i].parent=0;
		    ht[i].parent=ht[i].lchild=ht[i].rchild=0;
	}
	for(i=n+1;i<=m;i++)
	{
		huffmanselect(ht,i-1,&s1,&s2);
		ht[s1].parent=i;
		ht[s2].parent=i;
		ht[i].lchild=s1;
		ht[i].rchild=s2;
		ht[i].weight=ht[s1].weight+ht[s2].weight;
		a[o++]=ht[i].weight;//将每一次构造出的根存在数组中
	}
}
int main()
{
	int n,i,j,s=0;
	htnode ht[N+1];
	htcode hc[N+1];
	cin>>n;
	for(i=1;i<=n;i++)
	{
		cin>>hc[i].weight;
	}
	huffmantree(ht,hc,n);
    for(j=0;j<o;j++)
	{
        s+=a[j];
	}
	cout<<s<<endl;
	return 0;
}
//第一种方法：哈夫曼树
//第二种方法：优先队列的使用
#include<stdio.h>
#include<queue>
#include<algorithm>
using namespace std;
int main()
{
	int num;
	int n,i,a;
	priority_queue<int>plank;//<优先队列的使用>从小到大的顺序优先级队列
	long long int sum;
	while(scanf("%d",&n)!=EOF)
	{
		sum=0;
		while(n--)
		{
			scanf("%d",&num);
			plank.push(-num);
		}

	while(plank.size()!=1)
	{
		a=plank.top();
		plank.pop();
		a+=plank.top();
		sum+=a;
		plank.pop();
		plank.push(a);
	}
	plank.pop();
	printf("%lld\n",-sum);
	}
	return 0;
}

SDUTOJ 2127 树-堆结构练习——合并果子之哈夫曼树