【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[], lens[];

 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=; i<; ++i) {
         if(x & (<<i))
             ++lens[i];
     }
 }

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

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

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

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

     while (Q.size() > ) {
         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") == )
             break;
         bfs();
         len = strlen(s);
         sum = len<<;
         ans = ;
         for (int i=; i<; ++i)
             if (cnt[i])
                 ans += cnt[i]*lens[i];

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

     return ;
 }