Hdu 1053 Entropy

 

可以与Hdu 2527 用一样水过，因为这里不需要求编码，但我写这一题主要是为了学习哈弗曼建树，所以也用建树的写了一遍。

CODE：

 

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <queue>
using namespace std;

#define MAXN 1001
priority_queue<int , vector<int>, greater<int> > q;

char str[MAXN];
int huf[MAXN];
int len;

void solve()
{
    int ans = 0, a, b;
    while(q.size() != 1)
    {
        a = q.top(); q.pop();
        b = q.top(); q.pop();
        q.push(a+b);
        ans += (a+b);
    }
    printf("%d %d %.1lf\n", len*8, ans, len*8.0/ans);
}

void init()
{
    while(!q.empty()) q.pop();
    memset(huf, 0, sizeof(huf));
}

int main()
{
    while(scanf("%s", str) && strcmp(str, "END"))
    {
        init();
        len = strlen(str);
        for(int i = 0; i < len; i++)
        {
            huf[str[i]]++;
        }
        int ans1 = len*8;
        for(int i = 0; i < 100; i++) if(huf[i])
        {
            q.push(huf[i]);
        }
        if(q.size() == 1)
        {
            printf("%d %d 8.0\n", ans1, len);
            continue;
        }
        solve();
    }
    return 0;
}

CODE：

 

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <queue>
using namespace std;

const int MAXN = 1010;

struct node
{
    int data;
    int dep;
    node *L, *R;
    node()
    {
        data = 0;
        dep = 0;
        L = NULL;
        R = NULL;
    }
    bool operator <(node a) const
    {
        return a.data < data;
    } //重载小于号 
};

int ans;
char str[MAXN];
int huf[MAXN];

priority_queue<node> Q;

void BuildHuffman()
{
    node *p, *q, *T;
    while(Q.size() != 1)
    {
        p = new node();
        q = new node();
        T = new node();
        *p = Q.top(); Q.pop();
        *q = Q.top(); Q.pop();
        T->data = p->data + q->data;
        T->L = p, T->R = q;
        Q.push(*T);
    }
    return ;
}

queue<node> q;

void solve()
{
    node root;
    root = Q.top(); Q.pop();
    root.dep = 0;
    q.push(root);
    while(!q.empty())
    {
        node x = q.front(); q.pop();
        if(x.L)
        {
            x.L->dep = x.dep + 1;
            q.push(*(x.L));
        }
        if(x.R)
        {
            x.R->dep = x.dep + 1;
            q.push(*(x.R));
        }
        if(!x.L && !x.R)
        {
            ans += x.dep * x.data;
        }
    }
}

/*void dfs(node *p, int dep)
{
    if(!p->L && !p->R)
    {
        ans += p->data * dep;
    }
    if(p->L)
    {
        dfs(p->L, dep+1);
    }
    if(p->R)
    {
        dfs(p->R, dep+1);
    }
}*/

void init()
{
    ans = 0;
    while(!Q.empty()) Q.pop();
    while(!q.empty()) q.pop();
    memset(huf, 0, sizeof(huf));
}

int main()
{
    while(scanf("%s", str) && strcmp(str, "END"))
    {
        init();
        int len = strlen(str);
        for(int i = 0; str[i]; i++)
        {
            huf[str[i]]++;
        }
        for(int i = 0; i < 100; i++) if(huf[i])
        {
            node t;
            t.data = huf[i];
            Q.push(t);
        }
        if(Q.size() == 1) //特判
        {
            printf("%d %d 8.0\n", len*8, len);
            continue;
        }
        BuildHuffman();
        solve();
        //dfs(root, 0); 用DFS也可以实现 
        printf("%d %d %.1lf\n", len*8, ans, len*8.0/ans);
    }
    return 0;
}