HDU

字典树：问是否在给出的二进制中能找到前缀码。

#include<stdio.h>#include<string.h>#include<stdlib.h>#include<iostream>#include<algorithm>using namespace std;struct node{int x;node *next[22];node(){x=0;for(int i=0;i<2;i++)next[i]=NULL;}};node root;bool update(char *s){int k1=0,k2=1;int l=strlen(s);int id=0;node *p=&root;for(int i=0;i<l;i++){if(p->x==1)k2=0;id=s[i]-'0';if(p->next[id]==NULL){k1=1;node *q=new node;p->next[id]=q;}p=p->next[id];}p->x=1;return k1&&k2;}int freedom(node *p){int i=0;    for(i=0;i<2;i++)    if(p->next[i]!=NULL) freedom(p->next[i]);    if(p==&root){    for(int j=0;j<2;j++)    p->next[j]=NULL;    p->x=0;}else{delete(p);}return 0;}int main(void){int i,j,k=1,kk=1,t=1;char s[20];while(scanf("%s",s)!=EOF){if(s[0]=='9'){if(kk==1)printf("Set %d is immediately decodable\n",t++);elseprintf("Set %d is not immediately decodable\n",t++);k=1;kk=1;freedom(&root);}else{k=update(s);if(k==0)kk=0;}}return 0;}