题目链接: http://poj.org/problem?id=3630
思路分析:
求在字符串中是否存在某个字符串为另一字符串的前缀:
即对于某个字符串而言,其是否为某个字符串的前缀,或存在某个其先前的字符串为其前缀;
(1)若该字符串为某个字符串前缀,则存在一条从根节点到该字符串的最后一个字符串的路径;
(2)若存在某个字符串为该字符串前缀,则在该字符串的查找路径中存在一条子路径,路径的最后的结点的endOfWord
标记为true,表示存在某个字符串为其前缀;
代码:
#include <iostream> using namespace std; const int MAX_N = 10; struct Trie { bool endOfWord; Trie *next[MAX_N]; Trie() { for (int i = 0; i < MAX_N; ++i) next[i] = NULL; endOfWord = false; } }; int nodeCount = 0; Trie *root = NULL; Trie memory[600000]; bool insertAndJudge(char *word) { Trie *cur = root, *next; int len = strlen(word); for (int i = 0; i < len; ++ i) { int k = word[i] - '0'; if (cur->next[k] == NULL) { next = &memory[nodeCount++]; cur->next[k] = next; cur = cur->next[k]; } else if (i == len - 1 || cur->next[k]->endOfWord == true) return false; else cur = cur->next[k]; } cur->endOfWord = true; return true; } int main() { int t; cin >> t; while (t--) { int n; bool flag = true; char word[15]; nodeCount = 0; memset(memory, 0, sizeof(memory)); root = &memory[nodeCount++]; cin >> n; while (n--) { scanf("%s", word); if (flag) flag = insertAndJudge(word); } if (flag) cout << "YES" << endl; else cout << "NO" << endl; } return 0; }