POJ 1521 Entropy

霍夫曼树

#include<cstdio> #include<string.h> #include<iostream> #include<string> using namespace std; #define LEFT(i) 2*i #define RIGHT(i) 2*i+1 #define PARENT(i) i/2 int heapsize,root; int finalcode[200]; struct Word{ int num,number; double freq; }word[200]; struct Node{ int num,l,r; bool leaf; }node[200]; void exchange(int s,int t){ int tem1; double tem2; int tem3; tem1=word[s].num; tem2=word[s].freq; tem3=word[s].number; word[s].num=word[t].num; word[s].freq=word[t].freq; word[s].number=word[t].number; word[t].num=tem1; word[t].freq=tem2; word[t].number=tem3; } void min_heap(int i){ int l,r,largest; l=LEFT(i); r=RIGHT(i); if(l>heapsize && r>heapsize) return; if(l<=heapsize && word[l].freq<word[i].freq) largest=l; else largest=i; if(r<=heapsize && word[r].freq<word[largest].freq) largest=r; if(largest!=i){ exchange(i,largest); min_heap(largest); } } void init_heap(){ int i; for(i=heapsize/2;i;i--){ min_heap(i); } } void insert(){ exchange(1,heapsize); min_heap(1); } void clear(){ exchange(1,heapsize); heapsize--; min_heap(1); } void addedge(int parent,int l,int r,int lmark,int rmark){ node[parent].leaf=0; node[parent].l=lmark; node[parent].r=rmark; if(l!=-1){ node[lmark].leaf=1; node[lmark].num=l; } if(r!=-1){ node[rmark].leaf=1; node[rmark].num=r; } } void code(int now,int i){ int j; if(node[now].leaf){ finalcode[node[now].num]=i; return; } code(node[now].l,i+1); code(node[now].r,i+1); } int main(){ char temp; int i,times[200]; int totalwords,nodes; string str; while(cin>>str && !(str=="END")){ memset(times,0,sizeof(times)); totalwords=0; for(i=0;i<str.size();i++){ temp=str[i]; times[temp]++; totalwords++; } heapsize=0; for(i=0;i<=130;i++){ if(times[i]){ word[++heapsize].number=-1; word[heapsize].num=i; word[heapsize].freq=(double)times[i]/totalwords; } } nodes=0; init_heap(); while(heapsize>1){ int l,r,lmark,rmark; double fl,fr; l=word[1].num; fl=word[1].freq; if(word[1].number==-1){ ++nodes; lmark=nodes; } else lmark=word[1].number; clear(); r=word[1].num; fr=word[1].freq; if(word[1].number==-1){ ++nodes; rmark=nodes; } else rmark=word[1].number; clear(); word[++heapsize].freq=fl+fr; word[heapsize].num=-1; word[heapsize].number=++nodes; insert(); addedge(nodes,l,r,lmark,rmark); } root=nodes; if(nodes) code(root,0); else finalcode[word[1].num]=1; int total1=0,total2=0; for(i=0;i<=130;i++){ if(times[i]){ total1+=times[i]*8; total2+=times[i]*finalcode[i]; } } printf("%d %d %.1f\n",total1,total2,(double)total1/total2); } }