題意：判斷一組字串中是否有兩個串A和串B，且A是B的字首，通過將串依次插入Trie即可判斷當前串是否是前面串的字首，和前面串是否有當前串的字首。

#include <cstdio>
#define MAX_N	200005

int N, NEX;
struct Node{
	Node* ch[2];
	bool isLeaf(){
		return !ch[0] && !ch[1];
	}
} nodes[MAX_N], *root;
Node* newNode(){
	nodes[NEX].ch[0] = nodes[NEX].ch[1] = NULL;
	return nodes + NEX++;
}

bool insert(Node* p, const char* s)
{
	bool newed = false;
	for(; *s; ++s){
		Node*& q = p->ch[*s - '0'];
		if(!q){
			q = newNode();
			newed = true;
		}
		else if(!newed && q != root && q->isLeaf()) return true;
		p = q;
	}
	return !newed;
}

int main()
{
	int kase = 0;
	char s[12];
	bool foundPrefix;
	while(gets(s)){
		++kase;
		NEX = 0;
		root = newNode();
		foundPrefix = false;
		for(; s[0] != '9' && !foundPrefix; gets(s)) foundPrefix = insert(root, s);
		while(s[0] != '9') gets(s);
		if(foundPrefix) printf("Set %d is not immediately decodable\n", kase);
		else printf("Set %d is immediately decodable\n", kase);
	}
	return 0;
}