#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
int n,m;
int map[501][501];
int prenode[501];
int ans[501];
int L;
void topsort()
{
int i,j,k;
L=0;
for(i=1;i<=n;i++)//n個節點,共n次
{
for(j=1;j<=n;j++)
{
if(prenode[j]==0)
{
ans[L++]=j;
prenode[j]--;
for(k=1;k<=n;k++)
{
if(map[j][k])
prenode[k]--;
}
// for(int f=1;f<=n;f++)printf("**%d %d\n",f,prenode[f]);
break;
}
}
if(j==n+1){
cout<<"存在環"<<endl;
return;
}
}
}
int main()
{
while(cin>>n>>m)
{
int i,a,b;
memset(map,0,sizeof(map));
memset(prenode,0,sizeof(prenode));
while(m--)
{
cin>>a>>b;
if(!map[a][b]){
map[a][b]=1;
prenode[b]++;
}
}
topsort();
for(i=0;i<L;i++)
{
if(i<L-1)printf("%d ",ans[i]);
else printf("%d\n",ans[i]);
}
}
return 0;
}
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<string>
#include<queue>
using namespace std;
int n,m;
int prenode[27];//第i個節點前驅節點數,即第i個節點的度數
bool map[27][27];//記錄關係網
bool isused[27];//節點是否全部被用完
bool isexist[27];//節點是否存在
string path;
int f1,f2;
/*
1. Sorted sequence determined after 4 relations: ABCD.
每次要保證入度爲0的點只有1個 且 n個點全部用完且僅被用一次
2. Inconsistency found after 2 relations.
存在環
3. Sorted sequence cannot be determined.
關係不能確定,條件不足
*/
int Cnt()
{
int sum=0;
for(int i=0;i<27;i++)if(isexist[i])sum++;
return sum;
}
int floyd()
{
int i,j,k;
for(k=0;k<n;k++)
{
for(i=0;i<n;i++)
for(j=0;j<n;j++)
map[i][j]=map[i][j]||map[i][k]&&map[k][j];
}
for(i=0;i<n;i++)
if(map[i][i])return 0; //有環
return 1; //無環
}
bool ifused()//節點是否全部被用完
{
int f=1;
for(int i=0;i<n;i++){
if(!isused[i]){
f=0;
break;
}
}
return f;
}
void topsort()
{
if(!floyd()){
f2=1;
return;
}
queue<int>q;
int i,j;
path="";
memset(prenode,0,sizeof(prenode));
memset(isused,0,sizeof(isused));
for(i=0;i<n;i++)
{
for(j=0;j<n;j++)
{
if(map[j][i])prenode[i]++;
}
if(isexist[i]&&!prenode[i]){
q.push(i);
/// printf(" %c\n",i+'A');
}
}
if(q.empty()){
f2=1;//存在環
return;
}
if(q.size()>1){
return;//關係無法確定
}
int nnow=Cnt();//計算當前節點數
/// printf(" nnow=%d\n",nnow);
int cnt=0;//記錄所用字母數
while(nnow--)
{
if(q.empty())
{
f2=1;//存在環
/// printf("huan2\n");
return;
}
int temp=q.front();
q.pop();
prenode[temp]--;
isused[temp]=1;
path+=(char)(temp+'A');
/// printf("* %c\n",temp+'A');
cnt++;
for(i=0;i<n;i++){
if(map[temp][i]){
prenode[i]--;
if(!prenode[i])q.push(i);
}
}
if(q.size()>1)return;
}
if(cnt==n&&ifused())f1=1;
}
int main()
{
freopen("data.in","r",stdin);
freopen("data.out","w",stdout);
while(cin>>n>>m&&(n+m))
{
char a,b,c;
memset(map,0,sizeof(map));
memset(isexist,0,sizeof(isexist));
int i,ans;
f1=f2=0;
for(i=1;i<=m;i++)
{
cin>>a>>c>>b;
a=a-'A';
b=b-'A';
map[a][b]=1;
isexist[a]=1;
isexist[b]=1;
if(f1||f2)continue;
topsort();
if(f2==1)ans=i;
if(f1==1)ans=i;
}
if(f1==1)cout<<"Sorted sequence determined after "<<ans<<" relations: "<<path<<"."<<endl;
else if(f2==1)cout<<"Inconsistency found after "<<ans<<" relations."<<endl;
else cout<<"Sorted sequence cannot be determined."<<endl;
}
return 0;
}
ZOJ1060 拓撲排序,錯了好幾次
G<F
A<B
B<C
C<D
D<F
F<B
D<E
#include<cstdio>
#include<cstring>
#include<iostream>
#include<vector>
using namespace std;
#define N 27
vector<int>G[N],res,point;
int n,ru[N];
int topsort()
{
int i,j,k,p;
memset(ru,0,sizeof(ru));
for(i=0;i<n;i++)
{
for(j=0;j<G[i].size();j++)ru[G[i][j]]++;
}
int num,ans=0;
res.clear();
int flag=1;
while(1){
// for(i=0;i<point.size();i++)printf("-- %d %d\n",point[i],ru[point[i]]);
// printf("*****\n");
num=0;
for(i=0;i<point.size();i++)
{
if(ru[point[i]]==0)
{
num++;
p=point[i];
}
}
if(num==0)return -1;//huan?
if(num>1)flag=0;//tianjianbuzu?
ru[p]=-1;
ans++;
res.push_back(p);
if(ans==n&&flag)return 1;
for(i=0;i<G[p].size();i++)ru[G[p][i]]--;
if(ans==point.size())return -2;
}
return -2;//?
}
int main()
{
char ch[5];
int x,y,m,i;
while(~scanf("%d%d",&n,&m)&&(n+m))
{
int flag=0,t,k;
for(i=0;i<27;i++)G[i].clear();
point.clear();
for(k=1;k<=m;k++)
{
scanf("%s",&ch);
x=ch[0]-'A';
y=ch[2]-'A';
if(flag)continue;
for(i=0;i<point.size();i++)if(point[i]==x)break;
if(i==point.size())point.push_back(x);
for(i=0;i<point.size();i++)if(point[i]==y)break;
if(i==point.size())point.push_back(y);
for(i=0;i<G[x].size();i++)if(G[x][i]==y)break;//quchong
if(i<G[x].size())continue;
G[x].push_back(y);
t=topsort();
if(t==1)
{
printf("Sorted sequence determined after %d relations: ",k);
for(i=0;i<res.size();i++)printf("%c",res[i]+'A');
printf(".\n");
flag=1;
}
else if(t==-1)
{
printf("Inconsistency found after %d relations.\n",k);
flag=1;
}
}
if(!flag)printf("Sorted sequence cannot be determined.\n");
}
return 0;
}
/*
4 6
A<B
A<C
B<C
C<B
C<D
B<D
7 7
A<B
B<C
C<D
D<F
F<B
D<E
G<F
3 2
A<B
C<B
*/