hdu 3247 Resource Archiver(AC自动机+BFS+DP)

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题目链接：hdu 3247 Resource Archiver

题目大意：给定N个需要包含的串，M个不能包含的串，问说满足的最短字符串长度。

解题思路：直接对所有串建立AC自动机，不能满足的串用同一种标记即可。然后处理出所有属于需要包含串的单词节

点，用BFS处理出两两之间的距离，并且过程中是不能经过禁止节点。这样做的原因是节点的个数很多，如果对所有的

节点进行dp的话空间都不够。剩下的就是dp了。

#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <iostream>
#include <algorithm>

using namespace std;


typedef pair<int,int> pii;
const int maxn = 100005;
const int maxm = 1005;
const int sigma_size = 2;
const int inf = 0x3f3f3f3f;

struct Aho_Corasick {
    int sz, g[maxn][sigma_size];
    int tag[maxn], fail[maxn], vis[maxn];

    void init();
    int idx(char ch);
    void insert(char* str, int k);
    void getFail();
    void match(char* str);
    void put(int x, int y);

    queue<int> que;
    int K, pos[maxm], dis[maxn];
    int dp[maxm][1030], d[maxm][maxm];

    int solve();
    void BFS(int s);
    int DP();
}AC;

int N, M;
char w[1005];

int main () {
    while (scanf("%d%d", &N, &M) == 2 && N + M) {
        AC.init();
        for (int i = 1; i <= N; i++) {
            scanf("%s", w);
            AC.insert(w, i);
        }
        for (int i = 1; i <= M; i++) {
            scanf("%s", w);
            AC.insert(w, 0);
        }
        printf("%d\n", AC.solve());
    }
    return 0;
}

int Aho_Corasick::DP() {
    int E = (1<<N)-1;
    memset(dp, inf, sizeof(dp));
    dp[0][0] = 0;

    for (int i = 0; i < E; i++) {
        for (int u = 0; u < K; u++) {
            if (dp[u][i] == inf)
                continue;

            for (int v = 0; v < K; v++) {
                if (d[u][v] == inf)
                    continue;

                int s = i | (tag[pos[v]]>>1);
                dp[v][s] = min(dp[v][s], dp[u][i] + d[u][v]);
            }
        }
    }
    int ans = inf;
    for (int i = 0; i < K; i++)
        ans = min(ans, dp[i][E]);
    return ans;
}

void Aho_Corasick::BFS(int s) {
    memset(dis, inf, sizeof(dis));
    dis[pos[s]] = 0;
    que.push(pos[s]);

    while (!que.empty()) {
        int u = que.front();
        que.pop();

        for (int i = 0; i < sigma_size; i++) {
            int t = u;
            while (t && g[t][i] == 0)
                t = fail[t];
            t = g[t][i];

            if (tag[t]&1)
                continue;
            if (dis[t] > dis[u] + 1) {
                dis[t] = dis[u] + 1;
                que.push(t);
            }
        }
    }
    for (int i = 0; i < K; i++)
        d[s][i] = dis[pos[i]];
}

int Aho_Corasick::solve() {
    getFail();
    K = 0;
    pos[K++] = 0;
    for (int i = 1; i <sz; i++) {
        if (tag[i]>>1)
            pos[K++] = i;
    }
    for (int i = 0; i < K; i++)
        BFS(i);
    return DP();
}

void Aho_Corasick::init() {
    sz = 1;
    tag[0] = 0;
    memset(g[0], 0, sizeof(g[0]));
}

int Aho_Corasick::idx(char ch) {
    return ch - ‘0‘;
}

void Aho_Corasick::put(int x, int y) {
}

void Aho_Corasick::insert(char* str, int k) {
    int u = 0, n = strlen(str);

    for (int i = 0; i < n; i++) {
        int v = idx(str[i]);
        if (g[u][v] == 0) {
            vis[sz] = tag[sz] = 0;
            memset(g[sz], 0, sizeof(g[sz]));
            g[u][v] = sz++;
        }
        u = g[u][v];
    }
    tag[u] = (1<<k);
}

void Aho_Corasick::match(char* str) {
    int n = strlen(str), u = 0;
    for (int i = 0; i < n; i++) {
        int v = idx(str[i]);
        while (u && g[u][v] == 0)
            u = fail[u];

        u = g[u][v];

    }
}

void Aho_Corasick::getFail() {

    for (int i  = 0; i < sigma_size; i++) {
        int u = g[0][i];
        if (u) {
            fail[u] = 0;
            que.push(u);
        }
    }

    while (!que.empty()) {
        int r = que.front();
        que.pop();

        for (int i = 0; i < sigma_size; i++) {
            int u = g[r][i];

            if (u == 0) {
                g[r][i] = g[fail[r]][i];
                continue;
            }

            que.push(u);
            int v = fail[r];
            while (v && g[v][i] == 0)
                v = fail[v];

            fail[u] = g[v][i];
            tag[u] |= tag[fail[u]];
            //last[u] = tag[fail[u]] ? fail[u] : last[fail[u]];
        }
    }
}

hdu 3247 Resource Archiver(AC自动机+BFS+DP)

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原文地址：http://blog.csdn.net/keshuai19940722/article/details/41020595