Entropy （huffman) 优先队列）

http://acm.hdu.edu.cn/showproblem.php?pid=1053

Huffman问题利用STL中的priority_queue解决；

#include<stdio.h>
#include<iostream>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
using namespace std;

struct cmp
{
    bool operator()(const int a, const int b)
    {
        return a > b;
    }
};
int solve(string str)
{
    priority_queue< int,vector<int>,cmp >que;
    map<char, int> mymap;
    int i;
    for(i =0; i < str.size(); i++)
    {
        mymap[str[i]]++;
    }

    map<char,int>::iterator it = mymap.begin();
    while(it != mymap.end())
    {
        //printf("%c %d\n",it->first,it->second);
        que.push(it->second);
        it++;
    }

    int weight = 0;
    if(que.size() == 1)
        return que.top();

    while(que.size() != 1)
    {
        int a,b;
        a = que.top();
        que.pop();
        b = que.top();
        que.pop();

        weight += a+b;
        que.push(a+b);
    }
    return weight;
}
int main()
{
    int weight;
    string str;
    while(cin>>str)
    {
        if(str == "END")
            break;
        weight = solve(str);
        printf("%d %d %.1lf\n",8*str.size(),weight,8.0*str.size()/weight);
    }
    return 0;
}