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| #include <cstdio>
#include <map>
#include <queue>
#include <string>
#include <iostream>
using namespace std;
const int N = 210, M = 2e4 + 10, inf = 100;
bool vis[N];
string name[N];
int n, m, st, ed, d[N], cur[N];
int idx = -1, hd[N], nxt[M], edg[M], wt[M], cst[M];
void add(int a, int b, int c, int d)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
wt[idx] = c;
cst[idx] = d;
}
bool bfs()
{
for (int i = st; i <= ed; i++)
d[i] = -inf;
d[st] = 0;
cur[st] = hd[st];
queue<int> q;
q.push(st);
while (!q.empty())
{
int t = q.front();
q.pop();
vis[t] = false;
for (int i = hd[t]; ~i; i = nxt[i])
if (d[t] + cst[i] > d[edg[i]] && wt[i])
{
d[edg[i]] = d[t] + cst[i];
cur[edg[i]] = hd[edg[i]];
if (!vis[edg[i]])
{
q.push(edg[i]);
vis[edg[i]] = true;
}
}
}
return d[ed] != -inf;
}
int exploit(int x, int limit)
{
if (x == ed)
return limit;
int res = 0;
vis[x] = true;
for (int i = cur[x]; ~i && res < limit; i = nxt[i])
{
cur[x] = i;
if (d[edg[i]] == d[x] + cst[i] && wt[i] && !vis[edg[i]])
{
int t = exploit(edg[i], min(limit - res, wt[i]));
if (!t)
d[edg[i]] = -inf;
res += t;
wt[i] -= t;
wt[i ^ 1] += t;
}
}
vis[x] = false;
return res;
}
void dinic(int &flow, int &cost)
{
int f;
cost = 0, flow = 0;
while (bfs())
while (f = exploit(st, inf))
flow += f, cost += f * d[ed];
}
int main()
{
cin >> n >> m;
st = 0, ed = n << 1 | 1;
for (int i = st; i <= ed; i++)
hd[i] = -1;
map<string, int> f;
for (int i = 1; i <= n; i++)
{
cin >> name[i];
f[name[i]] = i;
}
add(st, 1, 2, 0);
add(1, st, 0, 0);
add(n, ed, 2, 0);
add(ed, n, 0, 0);
add(1, 1 + n, 2, 0);
add(1 + n, 1, 0, 0);
add(n, n + n, 2, 0);
add(n + n, n, 0, 0);
for (int i = 2; i < n; i++)
{
add(i, i + n, 1, 1);
add(i + n, i, 0, -1);
}
for (string a, b; m; m--)
{
cin >> a >> b;
int x = f[a], y = f[b];
if (x > y)
swap(x, y);
add(x + n, y, n, 0);
add(y, x + n, 0, 0);
}
int flow, cost;
dinic(flow, cost);
if (flow < 2)
{
cout << "No Solution!";
return 0;
}
cout << cost + 2 << endl;
vector<int> ans;
int p = 1 + n;
while (p != n + n)
{
ans.push_back(p - n);
for (int i = hd[p]; ~i; i = nxt[i])
if (edg[i] > 0 && edg[i] <= n && wt[i] < n && !vis[edg[i]])
{
vis[edg[i]] = true;
p = edg[i] + n;
break;
}
}
p = n;
while (p != 1)
{
ans.push_back(p);
for (int i = hd[p]; ~i; i = nxt[i])
if (edg[i] > n && edg[i] < ed && wt[i] && !vis[edg[i] - n])
{
vis[edg[i] - n] = true;
p = edg[i] - n;
break;
}
}
for (int i : ans)
cout << name[i] << endl;
cout << name[1];
return 0;
}
|