hdu 2457 DNA repair(AC自动机+DP)

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题目链接：hdu 2457 DNA repair

题目大意：给定一些DNA序列，表示带有疾病，现在给定一个DNA序列，要求修改最少的位置，使得DNA不带有疾病的

片段。

解题思路：AC自动机+DP，先将DNA片段建立AC自动机，然后在AC自动机上进行dp，dp[i][j]表示长度为i移动到j节点

修改了最少的步数。每次走到边如果和字符串不同，权值即为1；相同则为0。单词节点不能向后转移。

#include <cstdio>#include <cstring>#include <queue>#include <vector>#include <iostream>#include <algorithm>using namespace std;typedef long long ll;const int maxn = 1005;const int sigma_size = 4;const int inf = 0x3f3f3f3f;const char sign[5] = "ACGT";struct Aho_Corasick {    int sz, g[maxn][sigma_size];    int tag[maxn], fail[maxn], last[maxn];    int dp[maxn][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);    int solve(char* s);}AC;int N;char s[maxn];int main () {    int cas = 1;    while (scanf("%d", &N) == 1 && N) {        AC.init();        for (int i = 0; i < N; i++) {            scanf("%s", s);            AC.insert(s, i+1);        }        scanf("%s", s);        printf("Case %d: %d\n", cas++, AC.solve(s));    }    return 0;}int Aho_Corasick::solve(char* s) {    getFail();    int n = strlen(s);    memset(dp, inf, sizeof(dp));    dp[0][0] = 0;    for (int k = 0; k < n; k++) {        for (int i = 0; i < sz; i++) {            if (dp[k][i] == inf || tag[i] || last[i])                continue;            for (int j = 0; j < 4; j++) {                int u = i;                while (u && g[u][j] == 0)                    u = fail[u];                u = g[u][j];                int d = (sign[j] == s[k] ? 0 : 1);                if (dp[k+1][u] > dp[k][i] + d)                    dp[k+1][u] = dp[k][i] + d;            }        }    }    int ans = inf;    for (int i = 0; i < sz; i++) {        if (tag[i] || last[i])            continue;        ans = min(ans, dp[n][i]);    }    return ans == inf ? -1 : ans;}void Aho_Corasick::init() {    sz = 1;    tag[0] = 0;    memset(g[0], 0, sizeof(g[0]));}int Aho_Corasick::idx(char ch) {    if (ch == 'A')        return 0;    if (ch == 'C')        return 1;    if (ch == 'G')        return 2;    return 3;}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) {            tag[sz] = 0;            memset(g[sz], 0, sizeof(g[sz]));            g[u][v] = sz++;        }        u = g[u][v];    }    tag[u] = 1;}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];        if (tag[u])            put(i, u);        else if (last[u])            put(i, last[u]);    }}void Aho_Corasick::getFail() {    queue<int> que;    for (int i  = 0; i < sigma_size; i++) {        int u = g[0][i];        if (u) {            fail[u] = last[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];            last[u] = tag[fail[u]] ? fail[u] : last[fail[u]];        }    }}

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