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| #include <cstdio>
#include <queue>
#include <cstring>
#include <algorithm>
const int maxn = 2005;
const int S = 0;
const int T = 2001;
const int INF = 0x3f3f3f3f;
using namespace std;
struct E{
int to, nxt, f;
}e[maxn << 4]; int now[maxn], head[maxn], tot = 1;
void addedge(int u, int v, int f){
e[++tot].to = v, e[tot].nxt = head[u], e[tot].f = f;
head[u] = tot;
}
void ins(int u, int v, int f){
addedge(u, v, f); addedge(v, u, 0);
}
int dep[maxn];
bool bfs(){
queue <int> q; while (!q.empty()) q.pop(); q.push(S);
memset(dep, 0, sizeof dep); dep[S] = 1;
while (!q.empty()){
int cur = q.front(); q.pop();
for (int i = head[cur]; i; i = e[i].nxt){
int v = e[i].to;
if (dep[v] == 0 && e[i].f > 0){
dep[v] = dep[cur] + 1;
q.push(v);
}
}
}
return dep[T] > 0;
}
int dfs(int cur, int Max){
if (cur == T) return Max;
int flow = 0;
for (int i = head[cur]; i; i = e[i].nxt){
int v = e[i].to;
if (e[i].f > 0 && dep[v] == dep[cur] + 1){
int tmp = dfs(v, min(Max - flow, e[i].f));
flow += tmp;
e[i].f -= tmp;
e[i ^ 1].f += tmp;
if (flow == Max) return flow;
}
}
return flow;
}
int maxflow;
void Dinic(){
maxflow = 0;
while (bfs()) maxflow += dfs(S, INF);
}
int n, m, u[maxn], v[maxn], a[maxn], b[maxn];
int Min = INF, Max = 0, dex[maxn], last[maxn];
bool check(int mid){
memset(dex, 0, sizeof dex);
tot = 1; memset(head, 0, sizeof head);
for (int i = 1; i <= m; i++){
if (a[i] > mid && b[i] > mid) return false;
if (a[i] <= mid) dex[u[i]]--, dex[v[i]]++;
if (b[i] <= mid) ins(v[i], u[i], 1), last[i] = tot - 1;
else last[i] = 0;
} int sum = 0;
for (int i = 1; i <= n; i++){
if (dex[i] & 1) return false;
if (dex[i] > 0) ins(S, i, dex[i] >> 1), sum += dex[i];
else ins(i, T, (-dex[i]) >> 1);
}
Dinic();
return maxflow == (sum >> 1);
}
namespace SPJ{
struct E{
int to, nxt;
}e[::maxn << 1]; int head[maxn], dex[maxn], tot = 0;
void addedge(int u, int v){
e[++tot].to = v, e[tot].nxt = head[u];
head[u] = tot; ++dex[u]; ++dex[v];
}
bool vis[maxn];
deque <pair<int, int> > v[maxn], t[maxn];
void dfs(int cur){
if (dex[cur] == 0) return;
dex[cur]--;
for (int i = head[cur]; i; i = e[i].nxt){
if (!vis[i]){
vis[i] = 1; t[cur].push_back(make_pair(i,e[i].to));
dex[e[i].to]--; dfs(e[i].to);
break;
}
}
}
void solve(){
for (int i = 1; i <= ::n; i++){
if (dex[i] != 0) dfs(i);
for (int j = 1; j <= n; j++)
while (!t[j].empty()){
v[j].push_front(t[j].back()), t[j].pop_back();
}
}
int cur = 1;
while (!v[cur].empty()){
printf("%d ", v[cur].front().first); int tmp = v[cur].front().second;
v[cur].pop_front(); cur = tmp;
} puts("");
}
}
int main(){
scanf("%d%d", &n, &m);
for (int i = 1; i <= m; i++){
scanf("%d%d%d%d", u + i, v + i, a + i, b + i);
Min = min(Min, min(a[i], b[i])); Max = max(Max, max(a[i], b[i]));
if (a[i] > b[i]) swap(u[i], v[i]), swap(a[i], b[i]);
}
int l = Min, r = Max, ans = -1;
while (l <= r){
int mid = l + r >> 1;
if (check(mid)){
ans = mid, r = mid - 1;
memset(SPJ::head, 0, sizeof SPJ::head); SPJ::tot = 0;
memset(SPJ::dex, 0, sizeof SPJ::dex);
for (int i = 1; i <= m; i++)
if (last[i] != 0 && e[last[i]].f == 0) SPJ::addedge(v[i], u[i]);
else SPJ::addedge(u[i], v[i]);
}
else l = mid + 1;
}
if (ans == -1) puts("NIE");
else printf("%d\n", ans);
if (ans != -1) SPJ::solve();
return 0;
}
|