題目鏈接:
點我點我
題目:
Genealogical tree Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 2704 Accepted: 1816 Special JudgeDescription
The system of Martians' blood relations is confusing enough. Actually, Martians bud when they want and where they want. They gather together in different groups, so that a Martian can have one parent as well as ten. Nobody will be surprised by a hundred of children. Martians have got used to this and their style of life seems to them natural.Input
The first line of the standard input contains an only number N, 1 <= N <= 100 — a number of members of the Martian Planetary Council. According to the centuries-old tradition members of the Council are enumerated with the natural numbers from 1 up to N. Further, there are exactly N lines, moreover, the I-th line contains a list of I-th member's children. The list of children is a sequence of serial numbers of children in a arbitrary order separated by spaces. The list of children may be empty. The list (even if it is empty) ends with 0.Output
The standard output should contain in its only line a sequence of speakers' numbers, separated by spaces. If several sequences satisfy the conditions of the problem, you are to write to the standard output any of them. At least one such sequence always exists.Sample Input
5 0 4 5 1 0 1 0 5 3 0 3 0
Sample Output
2 4 5 3 1
Source
Ural State University Internal Contest October'2000 Junior Session這個題目是拓撲排序的入門題。。
首先在這裡一個講的非常好的鏈接:
傳送門點我點我
我用了兩種方法做這個題。
第一種是利用入度為0的點必然是前面的點,然後刪除從這個點到其他點的邊,最後一期輸出結果。。速度很快。
第二種是利用dfs搜索,直到搜索到已經訪問到的點,然後利用棧來保存。。最後利用棧的性質來輸出即可。。
第二中代碼為:
#include#include #include #include #include using namespace std; const int maxn=100+10; int vis[maxn],map[maxn][maxn]; int n,t; stack S; bool dfs(int u) { vis[u]=-1; for(int v=1;v<=n;v++) if(map[u][v]) { // if(vis[v]<0) return false; if(!vis[v]&&!dfs(v)) return false; } vis[u]=1; S.push(u); return true; } bool toposort() { memset(vis,0,sizeof(vis)); for(int u=1;u<=n;u++) { if(!vis[u]) { if(!dfs(u)) return false; } } return true; } int main() { int u; bool ok; while(scanf("%d",&n)!=EOF) { t=n; memset(map,0,sizeof(map)); for(int i=1;i<=n;i++) { while(1) { scanf("%d",&u); if(u==0) break; map[i][u]=1; } } ok=toposort(); if(ok) { while(!S.empty()) { int val=S.top(); if(t!=1) printf("%d ",val); else printf("%d\n",val); S.pop(); t--; } } } return 0; }
第一種方法代碼:
#include#include const int maxn=100+10; int map[maxn][maxn],into[maxn],ans[maxn],vis[maxn]; int pos; int main() { int n,u,temp; while(~scanf("%d",&n)) { pos=0; memset(map,0,sizeof(map)); memset(into,0,sizeof(into)); memset(vis,0,sizeof(vis)); for(int i=1;i<=n;i++) { while(1) { scanf("%d",&u); if(u==0) break; map[i][u]=1; } } for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) { if(map[i][j]) into[j]++; } for(int i=1;i<=n;i++) for(int j=1;j<=n;j++) { if(into[j]==0&&!vis[j]) { temp=j; vis[j]=1; ans[pos++]=temp; for(int m=1;m<=n;m++) { if(map[temp][m]) into[m]--; } } } for(int i=0;i