bzoj1195 [HNOI2006]最短母串 AC 自动机+状压+bfs
题目传送门
https://lydsy.com/JudgeOnline/problem.php?id=1195
题解
建立 AC 自动机,然后构建出 trie 图。
然后直接在 trie 图上走。但是我们需要经过每一个串。
所以我们处理一下每个点代表了哪些串,然后把状态加入进 bfs 状态。
然后 bfs 就可以了。
\(O(n)\)。
#include<bits/stdc++.h> #define fec(i, x, y) (int i = head[x], y = g[i].to; i; i = g[i].ne, y = g[i].to) #define dbg(...) fprintf(stderr, __VA_ARGS__) #define File(x) freopen(#x".in", "r", stdin), freopen(#x".out", "w", stdout) #define fi first #define se second #define pb push_back template<typename A, typename B> inline char smax(A &a, const B &b) {return a < b ? a = b, 1 : 0;} template<typename A, typename B> inline char smin(A &a, const B &b) {return b < a ? a = b, 1 : 0;} typedef long long ll; typedef unsigned long long ull; typedef std::pair<int, int> pii; template<typename I> inline void read(I &x) { int f = 0, c; while (!isdigit(c = getchar())) c == '-' ? f = 1 : 0; x = c & 15; while (isdigit(c = getchar())) x = (x << 1) + (x << 3) + (c & 15); f ? x = -x : 0; } const int N = 12 + 1; const int M = 50 + 1; const int NM = 12 * 50 + 1; const int NP = (1 << 12); const int NMP = 12 * 50 * ((1 << 12) - 1) + 1; int n, m, nod; int q[NMP], q2[NMP], fr[NM][NP]; char s[N], ans[NM]; struct Node { int c[26], fa, v; char s; } t[NM]; inline void ins(char *s, int id) { int n = strlen(s + 1), o = 0; for (int i = 1; i <= n; ++i) { if (!t[o].c[s[i] - 'A']) t[o].c[s[i] - 'A'] = ++nod, t[nod].s = s[i]; o = t[o].c[s[i] - 'A']; } t[o].v |= 1 << (id - 1); } inline void build() { int hd = 0, tl = 0; for (int i = 0; i < 26; ++i) if (t[0].c[i]) q[++tl] = t[0].c[i]; while (hd < tl) { int x = q[++hd]; t[x].v |= t[t[x].fa].v; for (int i = 0; i < 26; ++i) if (t[x].c[i]) t[t[x].c[i]].fa = t[t[x].fa].c[i], q[++tl] = t[x].c[i]; else t[x].c[i] = t[t[x].fa].c[i]; } } inline void work() { int hd = 0, tl = 1, S = (1 << n) - 1; q[tl] = 0, q2[tl] = 0, fr[0][0] = -1; while (hd < tl) { int x = q[++hd]; int s = q2[hd]; // dbg("x = %d, s = %d\n", x, s); for (int i = 0; i < 26; ++i) if (t[x].c[i]) { int y = t[x].c[i], ss = s | t[y].v; // dbg("y = %d, ss = %d\n", y, ss); if (!fr[y][ss]) { fr[y][ss] = hd, q[++tl] = y, q2[tl] = ss; // dbg("****** y = %d, ss = %d\n", y, ss); if (ss == S) { int len = 0, z = y, zs = ss, zz; while (~fr[z][zs]) ans[++len] = t[z].s, zz = fr[z][zs], z = q[zz], zs = q2[zz]; while (len) putchar(ans[len--]); puts(""); // dbg("*********\n"); return; } assert(fr[y][ss]); } } } } inline void init() { read(n); for (int i = 1; i <= n; ++i) scanf("%s", s + 1), ins(s, i); build(); // dbg("*************\n"); } int main() { #ifdef hzhkk freopen("hkk.in", "r", stdin); #endif init(); work(); fclose(stdin), fclose(stdout); return 0; }
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