POJ1056 IMMEDIATE DECODABILITY(Trie树)

IMMEDIATE DECODABILITYTime Limit: 1000MS      Memory Limit: 10000KTotal Submissions: 13123        Accepted: 6275DescriptionAn encoding of a set of symbols is said to be immediately decodable if no code for one symbol is the prefix of a code for another symbol. We will assume for this problem that all codes are in binary, that no two codes within a set of codes are the same, that each code has at least one bit and no more than ten bits, and that each set has at least two codes and no more than eight. Examples: Assume an alphabet that has symbols {A, B, C, D} The following code is immediately decodable: A:01 B:10 C:0010 D:0000 but this one is not: A:01 B:10 C:010 D:0000 (Note that A is a prefix of C) InputWrite a program that accepts as input a series of groups of records from standard input. Each record in a group contains a collection of zeroes and ones representing a binary code for a different symbol. Each group is followed by a single separator record containing a single 9; the separator records are not part of the group. Each group is independent of other groups; the codes in one group are not related to codes in any other group (that is, each group is to be processed independently).OutputFor each group, your program should determine whether the codes in that group are immediately decodable, and should print a single output line giving the group number and stating whether the group is, or is not, immediately decodable.Sample Input0110001000009011001000009Sample OutputSet 1 is immediately decodableSet 2 is not immediately decodable

裸的trie数，求几段由01组成的数字中是否存在公共前缀。

#include<iostream>#include<cstring>#include<cstdlib>#include<algorithm>#include<cctype>#include<cmath>#include<ctime>#include<string>#include<stack>#include<deque>#include<queue>#include<list>#include<set>#include<map>#include<cstdio>#include<limits.h>#define MOD 1000000007#define fir first#define sec second#define fin freopen("/home/ostreambaba/文档/input.txt", "r", stdin)#define fout freopen("/home/ostreambaba/文档/output.txt", "w", stdout)#define mes(x, m) memset(x, m, sizeof(x))#define Pii pair<int, int>#define Pll pair<ll, ll>#define INF 1e9+7#define Pi 4.0*atan(1.0)#define lowbit(x) (x&(-x))#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1typedef long long ll;typedef unsigned long long ull;const double eps = 1e-12;const int maxn = 50010;const int maxm = 200010;using namespace std;inline int read(){    int x(0),f(1);    char ch=getchar();    while (ch<'0'||ch>'9') {if (ch=='-') f=-1;ch=getchar();}    while (ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}struct Trie{    int tot,root,child[maxn][2];    bool flag[maxn];    void init(){        mes(child[0],0);        flag[0]=false;        root=tot=0;    }    void insert(const char *str){        int *cur=&root;        for(const char *p=str;*p;++p){            cur=&child[*cur][*p-'0'];            if(0==*cur){                *cur=++tot;                mes(child[tot],0);                flag[tot]=false;            }        }        flag[*cur]=true;    }    bool query(const char *str){        int *cur=&root;        for(const char *p=str;*p&&*cur;++p){            cur=&child[*cur][*p-'0'];        }        return (*cur&&flag[*cur]);    }};int main(){    //fin;    char str[20];    int k=0,t=0;    Trie tree;    tree.init();    while(~scanf("%s",str)){        if(str[0]=='9'){            for(int i=1;i<=tree.tot;++i){                if(tree.flag[i]){                    if(tree.child[i][0]||tree.child[i][1]){                        k=1;                        break;                    }                }            }            if(!k){                printf("Set %d is immediately decodable\n",++t);            }            else{                printf("Set %d is not immediately decodable\n",++t);            }            tree.init();            k=0;        }        else{            tree.insert(str);        }    }    return 0;}