【HDOJ】1053 Entropy

构造huffman编码，果断对字符进行状态压缩。

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

#define MAXN 255
char s[MAXN];
int cnt[27], lens[27];

typedef struct node_t {
    int v;
    int n;
    node_t() { }
    node_t(int vv, int nn) {
        v = vv; n = nn;
    }
    friend bool operator <(node_t a, node_t b) {
        return a.n > b.n;
    }
} node_t;

void addBits(int x) {
    for (int i=0; i<27; ++i) {
        if(x & (1<<i))
            ++lens[i];
    }
}

void bfs() {
    priority_queue<node_t> Q;
    int i;

    memset(cnt, 0, sizeof(cnt));
    memset(lens, 0, sizeof(lens));
    for (i=0; s[i]; ++i)
        if (s[i] == '_')
            ++cnt[26];
        else
            ++cnt[s[i]-'A'];

    for (i=0; i<27; ++i)
        if (cnt[i])
            Q.push(node_t(1<<i, cnt[i]));

    if (Q.size() == 1) {
        node_t a = Q.top();
        addBits(a.v);
        return ;
    }

    while (Q.size() > 1) {
        node_t a = Q.top();
        addBits(a.v);
        Q.pop();
        node_t b = Q.top();
        Q.pop();
        addBits(b.v);
        Q.push(node_t(a.v|b.v, a.n+b.n));
    }
}

int main() {
    int len, sum, ans;

#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif

    while (scanf("%s", s) != EOF) {
        if (strcmp(s, "END") == 0)
            break;
        bfs();
        len = strlen(s);
        sum = len<<3;
        ans = 0;
        for (int i=0; i<27; ++i)
            if (cnt[i])
                ans += cnt[i]*lens[i];

        printf("%d %d %.1lf
", sum, ans, sum*1.0/ans);
    }

    return 0;
}