poj 3769 DNA repair

/*2016.01.22
 *poj3769DNArepair.cpp
 * ac自动机+dp, 多模式匹配
 * 考虑存在这样的修改满足题意，则沿着修改后的字符串进行状态转移每一步都
 * 将到达安全的状态（不含病毒串为子串），满足最优子结构。假设：
 * c 为从状态from到to的字符，dp[i][to]表示第i步到达to状态最少需要改变的字符数，
 * 状态from 和 to 都要是安全的：
 * dp[i][to] = min(dp[i-1][from] + c != s[i], dp[i][to])
 */

#include <cstdio>
#include <map>
#include <string.h>
#include <algorithm>
using namespace std;

const int MAX = 1010, SZ = 4;
int dp[MAX], tmp[MAX], cur;
map<char, int> c2n;

class node {
public:
    int unsafe;
    node *next[SZ], *fail;
    void init(){
        memset(this, 0, sizeof(node));
    }
}ac[MAX], *q[MAX], *rt;

void Insert(char *s){
    int i=0, idx;
    node *p=rt;
    for(i=0; s[i]; ++i){
        idx = c2n[s[i]];
        if(p->next[idx] == NULL){
            p->next[idx] = &ac[cur];
            ac[cur++].init();
        }
        p = p->next[idx];
    }
    p->unsafe = 1;
}
//v1：
// void BuildAC(){
//     int h = 1, t = 0, i;
//     node *nd;
//     q[0] = rt;
//     rt->fail = NULL;
//     while(t < h){
//         for(i=0; i<SZ; ++i){
//             if(q[t]->next[i] == NULL) continue;
//             if(q[t] == rt) q[t]->next[i]->fail = rt;
//             else {
//                 nd = q[t]->fail;
//                 while(nd != NULL && nd->next[i] == NULL) nd = nd->fail;
//                 if(nd == NULL) q[t]->next[i]->fail = rt;
//                 else {
//                     q[t]->next[i]->fail = nd->next[i];
//                     q[t]->next[i]->unsafe |= nd->next[i]->unsafe;
//                 }
//             }
//             q[h++] = q[t]->next[i];
//         }
//         ++t;
//     }
// }
//v2：
void BuildAC(){
    int h=1, t=0, i;
    node *nd;
    q[0] = rt;
    rt->fail = NULL;
    while(t < h){
        for(i=0; i<SZ; ++i){
            if(q[t]->next[i] != NULL) q[h++] = q[t]->next[i];
            if(q[t] == rt){
                if(q[t]->next[i] == NULL) q[t]->next[i] = rt;
                else q[t]->next[i]->fail = rt;
            }
            else {
                nd = q[t]->fail;
                if(q[t]->next[i] == NULL) q[t]->next[i] = nd->next[i];
                else {
                    q[t]->next[i]->fail = nd->next[i];
                    q[t]->next[i]->unsafe |= nd->next[i]->unsafe;
                }
            }
        }
        ++t;
    }
}
int Solve(char *s){
    int *bef = dp, *aft = tmp, i, j, k, n = strlen(s);
    node *nd;
    memset(bef, 0, sizeof(dp));
    for(i=0; i<n; ++i){
        memset(aft, 0x4, sizeof(dp));
        for(j=0; j<cur; ++j)
            if(ac[j].unsafe == 0){
                for(k=0; k<SZ; ++k){
                    int idx = ac[j].next[k] - rt;
                    // nd = &ac[j];
                    // while(nd != rt && nd->next[k]==NULL) nd = nd->fail;
                    // if(nd->next[k] != NULL) idx = nd->next[k] - rt;
                    if(ac[idx].unsafe == 0){
                        aft[idx] = min(aft[idx], bef[j]+(c2n[s[i]]!=k));
                    }
                }
                //第一次动归从根出发
                if(i == 0) break;
            }
        swap(aft, bef);
    }
    n = MAX;
    for(i=0; i<cur; ++i)
        if(ac[i].unsafe == 0)
            n = min(n, bef[i]);
    return n == MAX ? -1 : n;
}

int main() {
    int i, n, t=0;
    char s[MAX];
    rt = ac;
    c2n['A'] = 0; c2n['C'] = 1; c2n['G'] = 2; c2n['T'] = 3;
    while(scanf("%d", &n), n){
        cur = 1;
        ac[0].init();
        for(i=0; i<n; ++i){
            scanf("%s", s);
            Insert(s);
        }
        scanf("%s",s);
        BuildAC();
        printf("Case %d: %d
", ++t, Solve(s));
    }
}

参考：

http://blog.sina.com.cn/s/blog_6635898a0102e1ig.html