poj 2186 Popular Cows 【强连通分量】
2017-02-19 13:47
417 查看
Popular Cows
Every cow's dream is to become the most popular cow in the herd. In a herd of N (1 <= N <= 10,000) cows, you are given up to M (1 <= M <= 50,000) ordered pairs of the form (A, B) that tell you that cow A thinks that cow B is popular. Since popularity is transitive, if A thinks B is popular and B thinks C is popular, then A will also think that C is popular, even if this is not explicitly specified by an ordered pair in the input. Your task is to compute the number of cows that are considered popular by every other cow. Input * Line 1: Two space-separated integers, N and M * Lines 2..1+M: Two space-separated numbers A and B, meaning that A thinks B is popular. Output * Line 1: A single integer that is the number of cows who are considered popular by every other cow. Sample Input 3 3 1 2 2 1 2 3 Sample Output 1 Hint Cow 3 is the only cow of high popularity. Source USACO 2003 Fall |
代码:
#include<cstdio>
#include<vector>
#include<cstring>
#include<algorithm>
using namespace std;
int n,m,cmp[10100];
vector<int> V[10100],FV[10100],vs;
bool used[10100];
void add_edge(int a,int b)
{
V[a].push_back(b);
FV[b].push_back(a);
}
void dfs(int v)
{
used[v]=true;
for (int i=0;i<V[v].size();i++)
{
if (!used[V[v][i]]) dfs(V[v][i]);
}
vs.push_back(v);
}
void rdfs(int v,int k)
{
used[v]=true;
cmp[v]=k;
for (int i=0;i<FV[v].size();i++)
{
if (!used[FV[v][i]]) rdfs(FV[v][i],k);
}
}
int main()
{
scanf("%d%d",&n,&m);
// while (~scanf("%d%d",&n,&m))
// {
int a,b;
// for (int i=1;i<=n;i++)
// {
// V[i].clear();
// FV[i].clear();
// }
vs.clear();
for (int i=0;i<m;i++)
{
scanf("%d%d",&a,&b);
add_edge(a,b);
}
memset(used,0,sizeof(used));
for (int i=1;i<=n;i++)
{
if(!used[i]) dfs(i);
}
memset(used,0,sizeof(used));
int k=1;
for (int i=vs.size()-1;i>=0;i--)
{
if(!used[vs[i]]) rdfs(vs[i],k++);
}
int ans=0;
for (int i=1;i<=n;i++)
{
if (cmp[i]==k-1)
{
m=i;
ans++;
}
}
memset(used,0,sizeof(used));
rdfs(m,0);
for (int i=1;i<=n;i++)
{
if (!used[i])
{
ans=0;
break;
}
}
printf("%d\n",ans);
//}
return 0;
}
相关文章推荐
- POJ 2186 Popular Cows (强连通分量)
- poj 2186 Popular Cows 强连通分量
- POJ 2186 Popular Cows(强连通分量分解)
- 【poj 2186】Popular Cows(强连通分量)
- poj 2186 Popular Cows(强连通分量,tarjan或Kosaraju)
- POJ2186 Popular Cows 【强连通分量】+【Kosaraju】+【Tarjan】+【Garbow】
- 【POJ 2186】Popular Cows(强连通分量_tarjan)
- POJ 2186 Popular Cows (强连通分量)
- POJ 2186 Popular Cows(强连通分量分解)
- poj 2186 Popular Cows (强连通分量 tarjan)
- POJ 2186 Popular Cows(korasaju Algorithm求强连通分量)
- POJ 2186 Popular Cows (强连通分量)
- POJ_2186_Popular Cows_强连通分量
- POJ 2186 Popular Cows 强连通分量 Kosaraju or tarjan
- poj 2186 Popular Cows (强连通分量 tarjan)
- POJ 2186 Popular Cows【强连通分量分解】
- POJ-2186 Popular Cows (强连通分量[Kosaraju])
- poj 2186 Popular Cows(强连通分量模板题,tarjan)
- poj 2186 Popular Cows Tarjan 强连通分量
- Popular Cows POJ - 2186 (强连通分量)