USACO prefix TrieTree + DP

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/*ID:kevin_s1PROG:prefixLANG:C++*/#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <vector>#include <map>#include <set>#include <algorithm>#include <cstdlib>#include <list>#include <cmath>using namespace std;#define sigma_size 26#define MAX_LEN 2000001//gobal variable====struct trie_node{trie_node* next[sigma_size];bool is_terminal;trie_node(){memset(next, 0, sizeof(next));is_terminal = false;}};struct Trie{trie_node* root;int size;int idx(char ch){return ch - 'A';}Trie(){root = new trie_node();size = 1;}void Insert(string str){trie_node* cur = root;int len = str.length();for(int i = 0; i < len; i++){int ch = idx(str[i]);if(cur->next[ch] == NULL){cur->next[ch] = new trie_node();}cur = cur->next[ch];}cur->is_terminal = true;}bool Query(string str){trie_node* cur = root;int len = str.length();for(int i = 0; i < len; i++){int ch = idx(str[i]);if(cur->next[ch] == NULL){return false;}elsecur = cur->next[ch];}if(cur->is_terminal)return true;elsereturn false;}};int DP[MAX_LEN];string S;//==================//function==========//==================int main(){freopen("prefix.in","r",stdin);freopen("prefix.out","w",stdout);Trie prefix;string str;char ch[201];while(scanf("%s",ch) && strcmp(ch, ".") != 0){str = ch;prefix.Insert(str);}str.clear();int c;while((c = getchar()) != EOF){if(!isspace(c))S = S + (char)c;}int Len = S.length();memset(DP, 0, sizeof(DP));DP[Len] = 0;for(int i = Len - 1; i >= 0; --i){for(int j = 1; j <= 10 && (i + j - 1) < Len; ++j){string sub = S.substr(i, j);if(prefix.Query(sub)){if(DP[i + j] + j > DP[j])DP[i] = DP[i + j] + j;}}}cout<<DP[0]<<endl;return 0;}