Sorting It All Out
| Time Limit: 1000MS | Memory Limit: 10000K | |
| Total Submissions: 33184 | Accepted: 11545 |
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.
Source
因为要求几个relation，所以没加一个进行一次topoSort
一旦遇到有环或者唯一有序就sign＝1，后面的关系一定要读完(后果自负)，如果最后sign==0说明没确定顺序
要打印方案，可以用char topo[]来保存，然而输出topo[]比一个个输出慢了16MS，并且还忘初始化了WA好几次
//
// main.cpp
// poj1094
//
// Created by Candy on 9/11/16.
// Copyright © 2016 Candy. All rights reserved.
// #include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int N=;
int n,m,ind[N],ch[N][N];
char tmp[],topo[N];
int q[N];
int topoSort(){
int flag=;//only sorted
int indt[N];
for(int i=;i<=n;i++) indt[i]=ind[i];
for(int i=;i<=n;i++){//printf("%d %d %d \n",i,ind[i],ch[i][0]);
int zero=,u=;
for(int j=;j<=n;j++) if(indt[j]==) zero++,u=j;
if(zero==) return ;//circle
if(zero>) flag=;//no sorted
indt[u]--;
topo[i-]=(char)u+'A'-;
q[i-]=u;
for(int j=;j<=ch[u][];j++)
indt[ch[u][j]]--;
}
return flag;
}
int main(int argc, const char * argv[]) {
while(cin>>n>>m){
if(n==&&m==) break;
memset(ch,,sizeof(ch));
memset(ind,,sizeof(ind));
memset(topo,,sizeof(topo));
int sign=; for(int i=;i<=m;i++){
scanf("%s",tmp);
if(sign) continue;
int x=tmp[]-'A'+,y=tmp[]-'A'+;
ind[y]++;
ch[x][++ch[x][]]=y;
int flag=topoSort();
if(flag==){sign=;printf("Inconsistency found after %d relations.\n",i);}
if(flag==){
sign=;printf("Sorted sequence determined after %d relations: %s.\n",i,topo);
// printf("Sorted sequence determined after %d relations: ",i);
// for(int j=0;j<n;j++)
// printf("%c",q[j]+'A'-1);
// printf(".\n");
// sign=1;
}
}
if(!sign) printf("Sorted sequence cannot be determined.\n");
}
return ;
}