1 #include<cstdio> 2 #define INF 0x7FFFFFFF 3 #define MAXN 90010 4 int n, m, size; 5 int L[MAXN], R[MAXN], U[MAXN], D[MAXN], H[MAXN]; 6 int C[MAXN], S[MAXN]; 7 void Init() { 8 int i; 9 for (i = 0; i <= m; i++) { 10 S[i] = 0; 11 L[i + 1] = i; 12 R[i] = i + 1; 13 U[i] = D[i] = i; 14 } 15 R[m] = 0; 16 size = m + 1; 17 } 18 void Link(int r, int c) { 19 U[size] = c; 20 D[size] = D[c]; 21 U[D[c]] = size; 22 D[c] = size; 23 if (H[r] < 0) 24 H[r] = L[size] = R[size] = size; 25 else { 26 L[size] = H[r]; 27 R[size] = R[H[r]]; 28 L[R[H[r]]] = size; 29 R[H[r]] = size; 30 } 31 S[c]++; 32 C[size++] = c; 33 } 34 void Remove(int c) { 35 int i, j; 36 R[L[c]] = R[c]; 37 L[R[c]] = L[c]; 38 for (i = D[c]; i != c; i = D[i]) { 39 for (j = R[i]; j != i; j = R[j]) { 40 U[D[j]] = U[j]; 41 D[U[j]] = D[j]; 42 S[C[j]]--; 43 } 44 } 45 } 46 void Resume(int c) { 47 int i, j; 48 R[L[c]] = c; 49 L[R[c]] = c; 50 for (i = D[c]; i != c; i = D[i]) { 51 for (j = R[i]; j != i; j = R[j]) { 52 U[D[j]] = j; 53 D[U[j]] = j; 54 S[C[j]]++; 55 } 56 } 57 } 58 bool Dance(int now) { 59 if (R[0] == 0) 60 return true; 61 int i, j, temp, c; 62 for (temp=INF,i = R[0]; i; i = R[i]) { 63 if(S[i]<temp) 64 { 65 temp=S[i]; 66 c=i; 67 } 68 } 69 Remove(c); 70 for(i=D[c];i!=c;i=D[i]) 71 { 72 for(j=R[i];j!=i;j=R[j]) 73 Remove(C[j]); 74 if(Dance(now+1)) 75 return true; 76 for(j=L[i];j!=i;j=L[j]) 77 Resume(C[j]); 78 } 79 Resume(c); 80 return false; 81 } 82 int main() { 83 int i, j, k; 84 while (~scanf("%d%d", &n, &m)) { 85 Init(); 86 for (i = 1; i <= n; i++) { 87 H[i] = -1; 88 for (j = 1; j <= m; j++) { 89 scanf("%d", &k); 90 if (k) 91 Link(i, j); 92 } 93 } 94 if (Dance(0)) 95 puts("Yes, I found it"); 96 else 97 puts("It is impossible"); 98 } 99 return 0; 100 }
