POJ1094 Sorting It All Out
POJ1094 Sorting It All Out
Time Limit: 1000MS Memory Limit: 10000K
Total Submissions: 18073 Accepted: 6145
Description
An ascending sorted sequence of distinct values is one in which some form of a less-than operator is used to order the elements from smallest to largest. For example, the sorted sequence A, B, C, D implies that A < B, B < C and C < D. in this problem, we will give you a set of relations of the form A < B and ask you to determine whether a sorted order has been specified or not.
Input
Input consists of multiple problem instances. Each instance starts with a line containing two positive integers n and m. the first value indicated the number of objects to sort, where 2 <= n <= 26. The objects to be sorted will be the first n characters of the uppercase alphabet. The second value m indicates the number of relations of the form A < B which will be given in this problem instance. Next will be m lines, each containing one such relation consisting of three characters: an uppercase letter, the character "<" and a second uppercase letter. No letter will be outside the range of the first n letters of the alphabet. Values of n = m = 0 indicate end of input.
Output
For each problem instance, output consists of one line. This line should be one of the following three:
Sorted sequence determined after xxx relations: yyy...y.
Sorted sequence cannot be determined.
Inconsistency found after xxx relations.
where xxx is the number of relations processed at the time either a sorted sequence is determined or an inconsistency is found, whichever comes first, and yyy...y is the sorted, ascending sequence.
Sample Input
4 6
A<B
A<C
B<C
C<D
B<D
A<B
3 2
A<B
B<A
26 1
A<Z
0 0
Sample Output
Sorted sequence determined after 4 relations: ABCD.
Inconsistency found after 2 relations.
Sorted sequence cannot be determined.
*******************************************************************
拓扑排序,第一次写,可惜不是一A是二A,5555.
#include<iostream> #include<string.h> #include<vector> using namespace std; int gra[30][30],n; vector< int >ls; int vis[30],mark[30]; void dfs( int s) { vis[s]++; if (vis[s]>=2) return ; for ( int i=0;i<n;i++) if (gra[s][i]) dfs(i); } int main() { int m,num; while (cin>>n>>m,n+m) { num=n; memset (gra,0, sizeof (gra)); memset (mark,0, sizeof (mark)); char str[10]; int flag=0; for ( int i=1;i<=m;i++) { cin>>str; if (flag) continue ; int one=str[0]- 'A' ,two=str[2]- 'A' ; if (mark[two]==0)num--; mark[two]++; gra[one][two]=1; memset (vis,0, sizeof (vis)); dfs(one); if (vis[one]>1) { flag=1; cout<< "Inconsistency found after " <<i<< " relations." <<endl; } if (num!=1) continue ; int temp[30]; memcpy (temp,mark, sizeof (mark)); ls.clear(); for ( int j=1;j<=n;j++) { int k=-1; for ( int l=0;l<n;l++) if (temp[l]==0) { k=l; break ; } if (k==-1) break ; ls.push_back(k); temp[k]=-1; for ( int l=0;l<n;l++) if (gra[k][l]) temp[l]--; } int gu=0; for ( int j=0;j<n-1;j++) { memset (vis,0, sizeof (vis)); dfs(ls[j]); if (vis[ls[j+1]]==0){gu=1; break ;} } if (ls.size()==n&&gu==0) { flag=1; cout<< "Sorted sequence determined after " <<i<< " relations: " ; for ( int j=0;j<n;j++) cout<<( char )(ls[j]+ 'A' ); cout<< "." <<endl; } } if (flag==0) cout<< "Sorted sequence cannot be determined." <<endl; } } |
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