POJ 3253 Fence Repair(构造Huffman Tree)

//构造Huffman Tree,非叶子节点值总和即为结果，用最小优先队列维护#include<iostream>#include<queue>using namespace std;priority_queue<int,vector<int>,greater<int> > q;//最小优先队列，用greater<int>作为比较函数即可，less<int>则为最大优先队列int main(){//freopen("in.txt","r",stdin);long long int ans = 0;int n,node,first,second,new_node;scanf("%d",&n);for(int i = 0;i < n;++i){scanf("%d",&node);q.push(node);}for(int i = 1;i <= n-1;++i)//对于构造n个叶子的Huffman Tree，只需n-1次结点构造，因为Huffman Tree是正则二元树，可以证明结点数目总比叶子数目少1{first = q.top();q.pop();second = q.top();q.pop();new_node = first + second;q.push(new_node);ans += new_node;}printf("%I64d/n",ans);//扑街结果原来是long long int的，还好有Discuss，不然真的不知道怎么老WA!return 0;}