HDU 1704 Rank floyd求传递闭包 || bfs

题目：

题意：

思路：

#include <bits/stdc++.h>

using namespace std;

const int N = 500 + 10, INF = 0x3f3f3f3f;
bool mp

;

void floyd(int n)
{
for(int k = 1; k <= n; k++)
for(int i = 1; i <= n; i++)
if(mp[i][k])
for(int j = 1; j <= n; j++)
mp[i][j] = mp[i][j] || (mp[i][k] && mp[k][j]);
}
int main()
{
int t, n, m;
scanf("%d", &t);
while(t--)
{
memset(mp, 0, sizeof mp);
scanf("%d%d", &n, &m);
int v, u;
for(int i = 1; i <= m; i++)
{
scanf("%d%d", &v, &u);
mp[v][u] = true;
}
floyd(n);
int ans = 0;
for(int i = 1; i <= n; i++)
for(int j = i+1; j <= n; j++)
if(! mp[i][j] && ! mp[j][i]) ans++;
printf("%d\n", ans);
}
return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int N = 500 + 10, INF = 0x3f3f3f3f;

struct edge
{
int to, next;
}g[N*N];

int cnt, head
;
bool vis
;
void add_edge(int v, int u)
{
g[cnt].to = u, g[cnt].next = head[v], head[v] = cnt++;
}
int bfs(int v)
{
queue<int> que;
memset(vis, 0, sizeof vis);
int tot = 0;
que.push(v), vis[v] = true;
while(! que.empty())
{
int v = que.front(); que.pop();
for(int i = head[v]; i != -1; i = g[i].next)
{
int u = g[i].to;
if(! vis[u]) que.push(u), vis[u] = true, tot++;
}
}
return tot;
}
int main()
{
int t, n, m;
scanf("%d", &t);
while(t--)
{
cnt = 0;
memset(head, -1, sizeof head);
scanf("%d%d", &n, &m);
int v, u;
for(int i = 1; i <= m; i++)
{
scanf("%d%d", &v, &u);
add_edge(v, u);
}
int num = 0;
for(int i = 1; i <= n; i++) num += bfs(i);
printf("%d\n", n * (n-1) / 2 - num);
}
return 0;
}