[SDOI2010]外星千足虫（高斯消元）

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 #include<bitset>
 5 #define writeln(x)  write(x),puts("")
 6 #define writep(x)   write(x),putchar(' ')
 7 using namespace std;
 8 inline int read(){
 9     int ans=0,f=1;char chr=getchar();
10     while(!isdigit(chr)){if(chr=='-') f=-1;chr=getchar();}
11     while(isdigit(chr)){ans=(ans<<3)+(ans<<1)+chr-48;chr=getchar();}
12     return ans*f;
13 }void write(int x){
14     if(x<0) putchar('-'),x=-x;
15     if(x>9) write(x/10);
16     putchar(x%10+'0');
17 }const int M=2005;
18 bitset<M> a[M];
19 int n,m,ans;
20 inline void Gauss(){
21     for(int i=1,now;i<=n;i++){now=i;
22         while(!a[now][i]&&now<=m) ++now;
23         if(now==m+1){return (void)(puts("Cannot Determine"));}
24         ans=max(ans,now);
25         if(now!=i) swap(a[now],a[i]);
26         for(int j=1;j<=m;j++)
27             if(i==j||!a[j][i]) continue;
28             else a[j]^=a[i];
29     }writeln(ans);
30     for(int i=1;i<=n;i++){
31         if(!a[i][n+1]) puts("Earth");
32         else puts("?y7M#");
33     }
34 }
35 int main(){
36     n=read(),m=read();
37     for(int i=1;i<=m;i++)
38         for(int j=1;j<=n+1;j++){
39             char chr;
40             while((chr=getchar())<'0'||chr>'1');
41             a[i][j]=chr-48;
42         }Gauss();
43     return 0;
44 }