nyoj 349 Sorting It All Out 【topo】



Sorting It All Out

时间限制：3000 ms | 内存限制：65535 KB

难度：3

描述
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.

输入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.

输出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.

样例输入

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

样例输出

Sorted sequence determined after 4 relations: ABCD.
Inconsistency found after 2 relations.
Sorted sequence cannot be determined.

分析：

先把字符串转换成acci值，然后topo以下就行了

代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
#include<queue>
#include<iostream>
#include<cmath>
#define mem(x,y) memset(x,y,sizeof(x))
#include<stack>
using namespace std;
const int maxn =35;
bool flag1,flag2;
int map[maxn][maxn];
int vis[maxn];
int tp[maxn];

void topo(int n)
{
int k=0,i,j,temp[maxn],m,id;
bool flag=false;
memset(temp,0,sizeof(temp));
for(i=0;i<n;i++)
temp[i]=vis[i];
for(i=0;i<n;i++)
{
m=0;
for(j=0;j<n;j++)
{
if(temp[j]==0)
{
m++;
id=j;
}
}
if(m==0)
{
flag2=true;
return;
}
if(m>1)
flag=true;
tp[k++]=id;
temp[id]=-1;
for(j=0;j<n;j++)
if(map[id][j]==1)
temp[j]--;
}
if(!flag)
flag1=true;
}

int main()
{
int n,m;
while(scanf("%d%d",&n,&m)&&(n||m))
{
mem(map,0);
mem(vis,0);
flag1=flag2=false;
int i,p;
char u,v,t;
for(i=1;i<=m;i++)
{
cin>>u>>t>>v;
if(!flag1&&!flag2)
{
map[u-'A'][v-'A']=1;
vis[v-'A']++;
topo(n);
p=i;
}
}
if(flag1)
{
printf("Sorted sequence determined after %d relations: ",p);
for(i=0;i<n;i++)
printf("%c",tp[i]+'A');
printf(".\n");
continue;
}
if(flag2)
{
printf("Inconsistency found after %d relations.\n",p);
continue;
}
printf("Sorted sequence cannot be determined.\n");
}
//system("pause");
return 0;
}

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