poj 1625 Censored! AC自动机+DP +高精度 + C艹 + java

挺简单的一道题，搞了很久，主要是用java写的时候对java不熟悉，各种错误都出来了，不过学到了不少

这题用DP去构造就可以了，另有一题加强版（poj 2778）题意一样，只不过需要用到矩阵乘法

dp[i][j]表示长度为i的串走到了j节点的方案数（不包含病毒串）

先献上java代码，输入问题要注意啊，可能有大于127的字符出现，java的读入很蛋疼，没好好学过java还真不知道要这么写，具体见代码

import java.math.*;
import java.util.*;
import java.io.*;
import java.util.*;

public class Main {
	int M = 110;
	int CD;
	int fail[] = new int[M];
	int Q[] = new int[M];
	int ch[][] = new int[M][55];
	int ID[] = new int[256];
	int sz;
	int flag[] = new int[M];
	String DIC;
	BigInteger dp[][] = new BigInteger[55][M];
	BigInteger ans;
	PrintStream out = System.out;
	int m;
	
	public void Init() {
		fail[0] = 0;
		flag[0] = 0;
		Arrays.fill(ch[0], 0);
		sz = 1;
		for (int i = 0; i < DIC.length(); i++)
			ID[DIC.charAt(i)] = i;
		CD = DIC.length();
	}

	public void Insert(String s) {
		int p = 0;
		for (int i = 0; i < s.length(); i++) {
			int c = ID[s.charAt(i)];
			if (ch[p][c] == 0) {
				Arrays.fill(ch[sz], 0);
				flag[sz] = 0;
				ch[p][c] = sz++;
			}
			p = ch[p][c];
		}
		flag[p] = 1;
	}

	void Construct() {
		int head = 0, tail = 0;
		for (int i = 0; i < CD; i++) {
			if (ch[0][i] != 0) {
				fail[ch[0][i]] = 0;
				Q[tail++] = ch[0][i];
			}
		}
		while (head != tail) {
			int u = Q[head++];
			for (int i = 0; i < CD; i++) {
				int v = ch[u][i];
				if (v != 0) {
					Q[tail++] = v;
					fail[v] = ch[fail[u]][i];
					flag[v] += flag[fail[v]];
				} else {
					ch[u][i] = ch[fail[u]][i];
				}
			}
		}
	}
    public void DP(){
    	for (int i = 0; i <= m; i++) {
			for (int j = 0; j <= sz; j++) {
				dp[i][j] = BigInteger.ZERO;
			}
		}
		dp[0][0] = BigInteger.ONE;
		for (int i = 0; i < m; i++) {
			for (int j = 0; j < sz; j++)
				if (dp[i][j].compareTo(BigInteger.valueOf(0)) == 1) {
					for (int k = 0; k < CD; k++) {
						if (flag[ch[j][k]] > 0 || flag[j] > 0)
							continue;
						dp[i + 1][ch[j][k]] = dp[i + 1][ch[j][k]].add(dp[i][j]);
					}
				}
		}
		ans = BigInteger.ZERO;
		for (int i = 0; i < sz; i++)
			ans = ans.add(dp[m][i]);
		out.println(ans);
    }
	public void solve() {
		int n, p ;
		try {
			BufferedReader cin = new BufferedReader(new InputStreamReader(System.in, "ISO-8859-1"));
			String[] args = cin.readLine().split(" ");
	        n = Integer.parseInt(args[0]);
	        m = Integer.parseInt(args[1]);
	        p = Integer.parseInt(args[2]);			
			DIC = cin.readLine();
			Init();
			for (int i = 0; i < p; i++) {
				String s=cin.readLine();
				Insert(s);
			}	
			Construct();
			DP();
		} catch(IOException e){
		}
	}

	public static void main(String args[]) {
		new Main().solve();
	}
}

c++代码

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