#include #define K_MAX 3 #define BIT_K_MAX 4 #define N_MAX 150 #define M_MAX 12000 const int bit[6] = {1, 2, 4, 8, 16, 32}; void chmin(int* a, int b) { if (*a > b) *a = b; } int lex_smaller(int a[], int b[]) { int i; for (i = 0; i <= a[0]; i++) { if (a[i] < b[i]) return 1; else if (a[i] > b[i]) return -1; } return 0; } void chlexmin(int a[], int b[]) { int i; if (lex_smaller(a, b) < 0) for (i = 0; i <= b[0]; i++) a[i] = b[i]; } typedef struct Edge { struct Edge *next; int v, id; unsigned int label; } edge; int complement_graph(int N, int M, int A[], int B[], edge* adj[], edge e[]) { static char adj_mat[N_MAX + 1][N_MAX + 1]; static int i, u, w; for (u = 1; u <= N; u++) for (w = u + 1; w <= N; w++) adj_mat[u][w] = 0; for (i = 1; i <= M; i++) { u = A[i]; w = B[i]; adj_mat[u][w] = 1; } for (u = 1; u <= N; u++) adj[u] = NULL; for (u = 1, i = 0; u <= N; u++) { for (w = u + 1; w <= N; w++) { if (adj_mat[u][w] != 0) continue; e[i].v = w; e[i].id = i; e[i].next = adj[u]; adj[u] = &(e[i++]); e[i].v = u; e[i].id = i; e[i].next = adj[w]; adj[w] = &(e[i++]); } } return i / 2; } #define MT_N 624 #define MT_M 397 #define MT_MATRIX_A 0x9908b0dfUL #define MT_UPPER_MASK 0x80000000UL #define MT_LOWER_MASK 0x7fffffffUL static unsigned int mt[MT_N]; static int mti = MT_N + 1; void init_genrand(unsigned int s) { mt[0] = s & 0xffffffffUL; for (mti = 1; mti < MT_N; mti++) { mt[mti] = (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); mt[mti] &= 0xffffffffUL; } } unsigned int genrand() { unsigned int y; static unsigned int mag01[2] = {0x0UL, MT_MATRIX_A}; if (mti >= MT_N) { int kk; if (mti == MT_N + 1) init_genrand(5489UL); for (kk = 0; kk < MT_N - MT_M; kk++) { y = (mt[kk] & MT_UPPER_MASK) | (mt[kk+1] & MT_LOWER_MASK); mt[kk] = mt[kk+MT_M] ^ (y >> 1) ^ mag01[y&0x1UL]; } for (; kk < MT_N - 1; kk++) { y = (mt[kk] & MT_UPPER_MASK) | (mt[kk+1] & MT_LOWER_MASK); mt[kk] = mt[kk+(MT_M-MT_N)] ^ (y >> 1) ^ mag01[y&0x1UL]; } y = (mt[MT_N-1] & MT_UPPER_MASK) | (mt[0] & MT_LOWER_MASK); mt[MT_N-1] = mt[MT_M-1] ^ (y >> 1) ^ mag01[y&0x1UL]; mti = 0; } y = mt[mti++]; y ^= (y >> 11); y ^= (y << 7) & 0x9d2c5680UL; y ^= (y << 15) & 0xefc60000UL; y ^= (y >> 18); return y; } #define POWX 4 // 3 -> 2^8, 4 -> 2^16, 5 -> 2^32 const unsigned int powd[6] = {2, 4, 16, 256, 65536}, powe[6] = {1, 2, 4, 8, 16, 32}; // Multiplication on a finite field of size 2^32 with XOR addition unsigned int nim_product(unsigned int A, unsigned int B) { if (A > B) return nim_product(B, A); else if (A <= 1) return A * B; static unsigned int memo[256][256] = {}; if (B < 256 && memo[A][B] != 0) return memo[A][B]; int i; for (i = 0; i < POWX; i++) { if (B == powd[i]) { if (A == powd[i]) return (B >> 1) * 3; else return A * B; } } unsigned int a[2], b[2], ans[2][2]; for (i = POWX - 1; i >= 0; i--) if (B > powd[i]) break; a[1] = A & (powd[i] - 1); a[0] = (A ^ a[1]) >> powe[i]; b[1] = B & (powd[i] - 1); b[0] = (B ^ b[1]) >> powe[i]; ans[0][0] = nim_product(a[0], b[0]); ans[0][1] = nim_product(a[0], b[1]); ans[1][0] = nim_product(a[1], b[0]); ans[1][1] = nim_product(a[1], b[1]); if (B < 256) { memo[A][B] = (ans[0][0] ^ ans[0][1] ^ ans[1][0]) * powd[i] ^ nim_product(ans[0][0], powd[i] >> 1) ^ ans[1][1]; return memo[A][B]; } else return (ans[0][0] ^ ans[0][1] ^ ans[1][0]) * powd[i] ^ nim_product(ans[0][0], powd[i] >> 1) ^ ans[1][1]; } // Computing the lexicographically-minimum shortest s-t path through K specified vertices in O(2^K L^2 M) time int lexmin_shortest_path_through_specified_vertices(int N, edge* adj[], edge e[], int s, int t, int K, char flag[], int ans[], int rep) { static int i, k_done, u, w, n, v[N_MAX + 1]; for (u = 1, n = 0, k_done = 0; u <= N; u++) { if (flag[u] > -2) v[++n] = u; // living vertices else if (flag[u] < -2) k_done |= bit[-3 - flag[u]]; // dead terminals } static int h, j, k, l, l_ans, cur, prev; static unsigned int dp[2][BIT_K_MAX][M_MAX * 2], tmp; static edge *p; for (j = 1, l_ans = n + 1; j <= rep; j++) { for (i = 1; i <= n; i++) { u = v[i]; for (p = adj[u]; p != NULL; p = p->next) { w = p->v; if (flag[w] > -2 && w < u) continue; p->label = genrand() % (powd[POWX] - 1) + 1; if (u != t && w != t) e[p->id ^ 1].label = p->label; else e[p->id ^ 1].label = genrand() % (powd[POWX] - 1) + 1; // around t } } for (k = 0; k < bit[K]; k++) { if ((k & k_done) != k_done) continue; for (i = 1; i <= n; i++) { u = v[i]; for (p = adj[u]; p != NULL; p = p->next) { dp[0][k][p->id] = 0; dp[0][k][p->id ^ 1] = 0; dp[1][k][p->id] = 0; dp[1][k][p->id ^ 1] = 0; } } for (p = adj[s]; p != NULL; p = p->next) { dp[0][k][p->id ^ 1] = 0; dp[1][k][p->id ^ 1] = 0; } } for (p = adj[t]; p != NULL; p = p->next) dp[0][k_done][p->id] = p->label; for (l = 1, cur = 1, prev = 0; l <= n; l++, cur ^= 1, prev ^= 1) { for (p = adj[s], tmp = 0; p != NULL; p = p->next) if (flag[p->v] > -2) tmp ^= dp[prev][bit[K] - 1][p->id ^ 1]; if (tmp != 0 || l == n) break; for (k = 0; k < bit[K]; k++) { if ((k & k_done) != k_done) continue; for (i = 1; i <= n; i++) { u = v[i]; h = flag[u]; if (u == s || u == t || (h >= 0 && (k & bit[h]) != 0)) continue; for (p = adj[u], tmp = 0; p != NULL; p = p->next) if (flag[p->v] > -2) tmp ^= dp[prev][k][p->id ^ 1]; for (p = adj[u]; p != NULL; p = p->next) { if (h < 0) dp[cur][k][p->id] = nim_product(tmp, p->label); else dp[cur][k | bit[h]][p->id] = nim_product(tmp ^ dp[prev][k][p->id ^ 1], p->label); if (flag[p->v] > -2) dp[prev][k][p->id ^ 1] = 0; } } } } if (tmp != 0) { if (l < l_ans) { for (p = adj[s], l_ans = l, ans[0] = N + 1; p != NULL; p = p->next) if (flag[p->v] > -2 && dp[prev][bit[K] - 1][p->id ^ 1] != 0) chmin(&(ans[0]), p->v); } else if (l == l_ans) { for (p = adj[s]; p != NULL; p = p->next) if (flag[p->v] > -2 && dp[prev][bit[K] - 1][p->id ^ 1] != 0) chmin(&(ans[0]), p->v); } } } if (l_ans > n) { for (i = 0; i < n; i++) ans[i] = 0; return n + 1; } else if (l_ans == 1) { ans[0] = s; return 1; } else { if (flag[ans[0]] == -1) flag[ans[0]] = -2; else flag[ans[0]] = -3 - flag[ans[0]]; return lexmin_shortest_path_through_specified_vertices(N, adj, e, ans[0], t, K, flag, &(ans[1]), rep) + 1; } } void solve(int N, int M, int X, int Y, int Z, int A[], int B[], int ans[]) { static int K = 2, T[K_MAX]; static edge *adj[N_MAX + 1] = {}, e[M_MAX * 2]; complement_graph(N, M, A, B, adj, e); T[0] = Y; T[1] = Z; static char flag[N_MAX + 1]; static int i, u; for (u = 1; u <= N; u++) flag[u] = -1; // nonterminals for (i = 0; i < K; i++) flag[T[i]] = i; // terminals ans[0] = lexmin_shortest_path_through_specified_vertices(N, adj, e, X, X, K, flag, &(ans[2]), 2); if (ans[0] <= N) ans[1] = X; } void print_ans(int N, int ans[]) { int i; if (ans[0] > N) { printf("-1\n"); return; } else printf("%d\n", ans[0]); for (i = 1; i <= ans[0]; i++) printf("%d ", ans[i]); printf("%d\n", ans[1]); } int main() { int i, N, M, X, Y, Z, A[M_MAX + 1], B[M_MAX + 1], ans[N_MAX + 2]; scanf("%d %d", &N, &M); scanf("%d %d %d", &X, &Y, &Z); for (i = 1; i <= M; i++) scanf("%d %d", &(A[i]), &(B[i])); solve(N, M, X, Y, Z, A, B, ans); print_ans(N, ans); fflush(stdout); return 0; }