ACM--Entrophy(优先队列建树+哈希)

//主要感悟:

//建哈夫曼树使用优先队列能够显著减少代码量，也比较容易实现。

//建立一个哈希表，每个字符与一个数字对应，这样编程比较方便

#include <iostream>#include<queue>#include<stdio.h>#include<string.h>#include<iomanip>using namespace std;struct Tree{int parent;int weight;    int order;     int code_lenth;}a[100];struct cmp{    bool operator ()(Tree &a,Tree &b){        return a.weight>b.weight;    }};int hash[200];int main(){priority_queue<Tree,vector<Tree>,cmp >q;string n;while(getline(cin,n),n!="END"){     int lenth=n.size();int j=1;//序号 memset(hash,0,sizeof(hash));a[1].order=j;a[1].weight=1;    hash[n[0]]=j;for(int i=1;i<lenth;i++){   int k=hash[n[i]];            //cout<<k<<" "<<j<<endl; if(k)a[k].weight++;else{a[++j].weight=1;a[j].order=j;hash[n[i]]=j;}}for(int i=1;i<=j;i++)   q.push(a[i]);   for(int i=j+1;i<=2*j-1;i++){       Tree temp;Tree temp1;Tree temp2;temp1=q.top();q.pop();temp2=q.top();q.pop();a[temp1.order].parent=i;a[temp2.order].parent=i;temp.weight=temp1.weight+temp2.weight;temp.order=i;temp.parent=0;a[i]=temp;q.push(temp);}q.pop();for(int i=1;i<=j;i++){     int sum=0;    int k=i;while(a[k].parent){sum++;k=a[k].parent;}a[i].code_lenth=sum;}int sum_lenth=0;for(int i=0;i<lenth;i++){int k=hash[n[i]];sum_lenth+=a[k].code_lenth;}if(j==1)  sum_lenth=lenth;cout<<lenth*8<<" "<<sum_lenth<<" ";      cout<<fixed<<setprecision(1)<<(float)lenth*8/(float)sum_lenth<<endl;}return 0;}