【HDOJ】1053 Entropy

构造huffman编码，果断对字符进行状态压缩。

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <queue>
 5 using namespace std;
 6
 7 #define MAXN 255
 8 char s[MAXN];
 9 int cnt[27], lens[27];
10
11 typedef struct node_t {
12     int v;
13     int n;
14     node_t() { }
15     node_t(int vv, int nn) {
16         v = vv; n = nn;
17     }
18     friend bool operator <(node_t a, node_t b) {
19         return a.n > b.n;
20     }
21 } node_t;
22
23 void addBits(int x) {
24     for (int i=0; i<27; ++i) {
25         if(x & (1<<i))
26             ++lens[i];
27     }
28 }
29
30 void bfs() {
31     priority_queue<node_t> Q;
32     int i;
33
34     memset(cnt, 0, sizeof(cnt));
35     memset(lens, 0, sizeof(lens));
36     for (i=0; s[i]; ++i)
37         if (s[i] == ‘_‘)
38             ++cnt[26];
39         else
40             ++cnt[s[i]-‘A‘];
41
42     for (i=0; i<27; ++i)
43         if (cnt[i])
44             Q.push(node_t(1<<i, cnt[i]));
45
46     if (Q.size() == 1) {
47         node_t a = Q.top();
48         addBits(a.v);
49         return ;
50     }
51
52     while (Q.size() > 1) {
53         node_t a = Q.top();
54         addBits(a.v);
55         Q.pop();
56         node_t b = Q.top();
57         Q.pop();
58         addBits(b.v);
59         Q.push(node_t(a.v|b.v, a.n+b.n));
60     }
61 }
62
63 int main() {
64     int len, sum, ans;
65
66 #ifndef ONLINE_JUDGE
67     freopen("data.in", "r", stdin);
68 #endif
69
70     while (scanf("%s", s) != EOF) {
71         if (strcmp(s, "END") == 0)
72             break;
73         bfs();
74         len = strlen(s);
75         sum = len<<3;
76         ans = 0;
77         for (int i=0; i<27; ++i)
78             if (cnt[i])
79                 ans += cnt[i]*lens[i];
80
81         printf("%d %d %.1lf\n", sum, ans, sum*1.0/ans);
82     }
83
84     return 0;
85 }