54 lines
1.3 KiB
C++
54 lines
1.3 KiB
C++
#include<cstdio>
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#include<cstring>
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#include<algorithm>
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#include<queue>
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#include<cassert>
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using namespace std;
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const int maxn=30;
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int n,m,d[maxn][maxn],in[maxn];
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char s[maxn][4];
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int solve(int m)
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{
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memset(d,0,sizeof(d));
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for(int i=1;i<=m;i++) d[s[i][0]-'A'+1][s[i][2]-'A'+1]=1;
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for(int k=1;k<=n;k++)
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for(int i=1;i<=n;i++)
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for(int j=1;j<=n;j++)
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d[i][j]|=d[i][k]&d[k][j];
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for(int i=1;i<=n;i++)
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for(int j=1;j<=n;j++)
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if(d[i][j]&&d[j][i]) { printf("Inconsistency found after %d relations.\n",m); return 1; }
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for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) if(i!=j&&d[i][j]+d[j][i]==0) return 0;
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printf("Sorted sequence determined after %d relations: ",m);
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for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) if(d[i][j]) in[j]++;
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queue<int> Q;
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for(int i=1;i<=n;i++) if(in[i]==0) Q.push(i);
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assert(Q.size()==1);
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while(Q.size())
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{
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int u=Q.front(); Q.pop();
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printf("%c",char(u-1+'A'));
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for(int i=1;i<=n;i++) if(d[u][i])
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{
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d[u][i]=0;
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in[i]--;
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if(in[i]==0) Q.push(i);
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}
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}
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puts(".");
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return 1;
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}
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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while(scanf("%d%d",&n,&m)==2&&n+m)
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{
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for(int i=1;i<=m;i++) scanf("%s",s[i]);
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for(int i=1;i<=m;i++) if(solve(i)) goto nxt;
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puts("Sorted sequence cannot be determined.");
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nxt:continue;
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}
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return 0;
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} |