#pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #pragma GCC optimize("inline") #include using namespace std; void*wmem; char memarr[96000000]; template inline void walloc1d(T **arr, int x, void **mem = &wmem){ static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1}; (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] ); (*arr)=(T*)(*mem); (*mem)=((*arr)+x); } template inline void walloc1d(T **arr, int x1, int x2, void **mem = &wmem){ walloc1d(arr, x2-x1, mem); (*arr) -= x1; } struct Rand{ unsigned x; unsigned y; unsigned z; unsigned w; Rand(void){ x=123456789; y=362436069; z=521288629; w=(unsigned)time(NULL); } Rand(unsigned seed){ x=123456789; y=362436069; z=521288629; w=seed; } inline unsigned get(void){ unsigned t; t = (x^(x<<11)); x=y; y=z; z=w; w = (w^(w>>19))^(t^(t>>8)); return w; } inline double getUni(void){ return get()/4294967296.0; } inline int get(int a){ return (int)(a*getUni()); } inline int get(int a, int b){ return a+(int)((b-a+1)*getUni()); } inline long long get(long long a){ return(long long)(a*getUni()); } inline long long get(long long a, long long b){ return a+(long long)((b-a+1)*getUni()); } inline double get(double a, double b){ return a+(b-a)*getUni(); } inline int getExp(int a){ return(int)(exp(getUni()*log(a+1.0))-1.0); } inline int getExp(int a, int b){ return a+(int)(exp(getUni()*log((b-a+1)+1.0))-1.0); } } ; inline int my_getchar_unlocked(){ static char buf[1048576]; static int s = 1048576; static int e = 1048576; if(s == e && e == 1048576){ e = fread_unlocked(buf, 1, 1048576, stdin); s = 0; } if(s == e){ return EOF; } return buf[s++]; } inline void rd(int &x){ int k; int m=0; x=0; for(;;){ k = my_getchar_unlocked(); if(k=='-'){ m=1; break; } if('0'<=k&&k<='9'){ x=k-'0'; break; } } for(;;){ k = my_getchar_unlocked(); if(k<'0'||k>'9'){ break; } x=x*10+k-'0'; } if(m){ x=-x; } } struct MY_WRITER{ char buf[1048576]; int s; int e; MY_WRITER(){ s = 0; e = 1048576; } ~MY_WRITER(){ if(s){ fwrite_unlocked(buf, 1, s, stdout); } } } ; MY_WRITER MY_WRITER_VAR; void my_putchar_unlocked(int a){ if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){ fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout); MY_WRITER_VAR.s = 0; } MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a; } inline void wt_L(char a){ my_putchar_unlocked(a); } inline void wt_L(int x){ int s=0; int m=0; char f[10]; if(x<0){ m=1; x=-x; } while(x){ f[s++]=x%10; x/=10; } if(!s){ f[s++]=0; } if(m){ my_putchar_unlocked('-'); } while(s--){ my_putchar_unlocked(f[s]+'0'); } } template inline S moddw_L(S a, const T b){ a %= b; if(a < 0){ a += b; } return a; } template void arrRot(int k, int N, T A[], T B[] = NULL, void *mem = wmem){ int i; int fg = 0; (k = moddw_L(k,N)); if(B==NULL){ walloc1d(&B, N, &mem); fg = 1; } for(i=(k);i<(N);i++){ B[i-k] = A[i]; } for(i=(0);i<(k);i++){ B[N-k+i] = A[i]; } if(fg){ for(i=(0);i<(N);i++){ A[i] = B[i]; } } } struct graph{ int N; int*es; int**edge; void setEdge(int N__, int M, int A[], int B[], void **mem = &wmem){ int i; N = N__; walloc1d(&es, N, mem); walloc1d(&edge, N, mem); for(i=(0);i<(N);i++){ es[i] = 0; } for(i=(0);i<(M);i++){ es[A[i]]++; es[B[i]]++; } for(i=(0);i<(N);i++){ walloc1d(&edge[i], es[i], mem); } for(i=(0);i<(N);i++){ es[i] = 0; } for(i=(0);i<(M);i++){ edge[A[i]][es[A[i]]++] = B[i]; edge[B[i]][es[B[i]]++] = A[i]; } } int anUndirectedCycle(int res[] = NULL, void *mem = wmem){ int i; int j; int k; int*arr; int*q; int qs; int qe; int*bk; if(res==NULL){ walloc1d(&res, N+1, &mem); } for(i=(0);i<(N);i++){ for(j=(0);j<(es[i]);j++){ if(edge[i][j]==i){ res[0] = res[1] = i; return 1; } } } walloc1d(&arr, N, &mem); walloc1d(&q, N, &mem); walloc1d(&bk, N, &mem); for(i=(0);i<(N);i++){ arr[i] = -1; } for(i=(0);i<(N);i++){ for(j=(0);j<(es[i]);j++){ k = edge[i][j]; if(arr[k] == i){ res[0] = i; res[1] = k; res[2] = i; return 2; } arr[k] = i; } } for(i=(0);i<(N);i++){ arr[i] = bk[i] = -1; } qs = qe = 0; q[qe++] = 0; arr[0] = 0; while(qs < qe){ i = q[qs++]; for(j=(0);j<(es[i]);j++){ k = edge[i][j]; if(arr[k]==-1){ arr[k] = arr[i] + 1; bk[k] = i; q[qe++] = k; continue; } if(arr[k] == arr[i] - 1){ continue; } qs = qe = 1; res[0] = i; q[0] = k; while(i!=k){ if(arr[i] > arr[k]){ res[qs++] = (i = bk[i]); } else{ q[qe++] = (k = bk[k]); } } reverse(res, res+qs); for(i=(0);i<(qe);i++){ res[qs++] = q[i]; } return qs - 1; } } return -1; } } ; unsigned long long HashMap_ullP_L[4]; template struct HashMap{ char*used; KEY*key; VAL*val; int mem; int n; int mask; int init_flag; VAL init_val; HashMap(){ mem = 0; init_flag = 0; } ~HashMap(){ free(); } void expand(int nn){ if(mem >= nn){ return; } if(mem){ free(); } mem = nn; used = new char[nn]; key = new KEY[nn]; val = new VAL[nn]; } void free(){ if(mem){ mem = 0; delete[] used; delete[] key; delete[] val; } } void init(int nn){ int i; n = 1; nn = nn + (nn + 1) / 2; while(n < nn){ n *= 2; } mask = n - 1; expand(n); for(i=(0);i<(n);i++){ used[i] = 0; } init_flag = 0; } void init(int nn, VAL ini){ int i; n = 1; nn = nn + (nn + 1) / 2; while(n < nn){ n *= 2; } mask = n - 1; expand(n); for(i=(0);i<(n);i++){ used[i] = 0; } init_flag = 1; init_val = ini; } inline int getHash(const int a){ unsigned long long d = a; d = (((d * HashMap_ullP_L[0]) >> 32) * HashMap_ullP_L[1]) & mask; return d; } inline int getHash(const unsigned a){ unsigned long long d = a; d = (((d * HashMap_ullP_L[0]) >> 32) * HashMap_ullP_L[1]) & mask; return d; } inline int getHash(const long long a){ unsigned long long d = a; d = (((((d * HashMap_ullP_L[0]) >> 32) * HashMap_ullP_L[1]) >> 32) * HashMap_ullP_L[2]) & mask; return d; } inline int getHash(const unsigned long long a){ unsigned long long d = a; d = (((((d * HashMap_ullP_L[0]) >> 32) * HashMap_ullP_L[1]) >> 32) * HashMap_ullP_L[2]) & mask; return d; } inline int getHash(const pair a){ unsigned long long d = (((unsigned long long)a.first) << 32) + ((unsigned long long)a.second); d = (((((d * HashMap_ullP_L[0]) >> 32) * HashMap_ullP_L[1]) >> 32) * HashMap_ullP_L[2]) & mask; return d; } inline VAL& operator[](const KEY a){ int k = getHash(a); for(;;){ if(used[k]==1 && key[k]==a){ break; } if(used[k]==0){ used[k] = 1; key[k] = a; if(init_flag){ val[k] = init_val; } break; } k = (k+1) & mask; } return val[k]; } inline bool exist(const KEY a){ int k = getHash(a); for(;;){ if(used[k]==1 && key[k]==a){ return true; } if(used[k]==0){ break; } k = (k+1) & mask; } return false; } template inline bool exist(const KEY a, S &res){ int k = getHash(a); for(;;){ if(used[k]==1 && key[k]==a){ res = val[k]; return true; } if(used[k]==0){ break; } k = (k+1) & mask; } return false; } } ; int H; int W; int N; int A[100000]; int B[100000]; HashMap,int> hs; graph g; int ress; int res[200000+1]; int arr[200000+1]; int main(){ int i; wmem = memarr; { int i; int j; int k; Rand rnd; for(i=(0);i<(20);i++){ rnd.get(2); } for(i=(0);i<(4);i++){ for(j=(0);j<(32);j++){ k = rnd.get(1,62); HashMap_ullP_L[i] |= (1ULL << k); } HashMap_ullP_L[i] |= (1ULL << 0); HashMap_ullP_L[i] |= (1ULL << 63); } } int x; int y; rd(H); rd(W); rd(N); { int Lj4PdHRW; for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){ rd(A[Lj4PdHRW]);A[Lj4PdHRW] += (-1); rd(B[Lj4PdHRW]);B[Lj4PdHRW] += (-1); } } hs.init(N); for(i=(0);i<(N);i++){ B[i] += 100000; } for(i=(0);i<(N);i++){ hs[{A[i],B[i]}] = i; } g.setEdge(200000, N, A, B); ress = g.anUndirectedCycle(res); if(ress==-1){ wt_L(ress); wt_L('\n'); return 0; } if(res[0] >= 100000){ arrRot(1,ress,res); res[ress] = res[0]; } for(i=(0);i<(ress);i++){ auto t_ynMSdg = ((res[i])); auto KrdatlYV = (( res[i+1])); x=t_ynMSdg; y=KrdatlYV; if(x > y){ swap(x, y); } ; arr[i] = hs[{x,y}]; } wt_L(ress); wt_L('\n'); { int ao_dF3pO; if(ress==0){ wt_L('\n'); } else{ for(ao_dF3pO=(0);ao_dF3pO<(ress-1);ao_dF3pO++){ wt_L(arr[ao_dF3pO]+1); wt_L(' '); } wt_L(arr[ao_dF3pO]+1); wt_L('\n'); } } for(i=(0);i<(ress);i++){ assert(A[arr[i%ress]] == A[arr[(i+1)%ress]] || B[arr[i%ress]] == B[arr[(i+1)%ress]]); } return 0; } // cLay version 20210717-1 [beta] // --- original code --- // int H, W, N, A[1d5], B[1d5]; // HashMap,int> hs; // graph g; // int ress, res[2d5+1], arr[]; // { // int x, y; // rd(H,W,N,(A--,B--)(N)); // hs.init(N); // rep(i,N) B[i] += 1d5; // rep(i,N) hs[{A[i],B[i]}] = i; // g.setEdge(2d5, N, A, B); // ress = g.anUndirectedCycle(res); // if(ress==-1) wt(ress), return 0; // if(res[0] >= 1d5) arrRot(1,ress,res), res[ress] = res[0]; // // rep(i,ress){ // (x, y) = (res[i], res[i+1]); // sortE(x, y); // arr[i] = hs[{x,y}]; // } // wt(ress); // wt(arr(ress)+1); // // rep(i,ress){ // assert(A[arr[i%ress]] == A[arr[(i+1)%ress]] || B[arr[i%ress]] == B[arr[(i+1)%ress]]); // } // // // rep(i,ress+1) wt("--", A[arr[i%ress]],B[arr[i%ress]]-1d5); // }