同 AcWing 2402 2-SAT 问题
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(2e6 + 10);
const int maxm(2e6 + 10);
int ecnt, head[maxn];
int tim, dfn[maxn], low[maxn];
int scnt, id[maxn];
bool vis[maxn];
stack<int> st;
struct edge {
int to, nxt;
} edges[maxm];
template<typename T = int>
inline const T read()
{
T x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 3) + (x << 1) + ch - '0';
ch = getchar();
}
return x * f;
}
template<typename T>
inline void write(T x, char c = false)
{
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) write(x / 10, false);
putchar(x % 10 + '0');
if (c) putchar(c);
}
void addEdge(int u, int v)
{
edges[ecnt].to = v;
edges[ecnt].nxt = head[u];
head[u] = ecnt++;
}
void tarjan(int u)
{
dfn[u] = low[u] = ++tim;
st.push(u);
vis[u] = true;
for (int i = head[u]; compl i; i = edges[i].nxt) {
int v = edges[i].to;
if (not dfn[v]) {
tarjan(v);
low[u] = min(low[u], low[v]);
} else if (vis[v]) {
low[u] = min(low[u], dfn[v]);
}
}
if (dfn[u] == low[u]) {
int v = -1;
++scnt;
do {
v = st.top();
st.pop();
vis[v] = false;
id[v] = scnt;
} while (u not_eq v);
}
}
int main()
{
#ifdef ONLINE_JUDGE
#else
freopen("input.txt", "r", stdin);
#endif
int n = read(), m = read();
memset(head, -1, sizeof head);
while (m--) {
int u = read() - 1, a = read(), v = read() - 1, b = read();
addEdge(u * 2 + not a, v * 2 + b);
addEdge(v * 2 + not b, u * 2 + a);
}
for (int i = 0; i < n * 2; ++i) {
if (not dfn[i]) {
tarjan(i);
}
}
bool flag = false;
for (int i = 0; i < n; ++i) {
if (id[i * 2] == id[i * 2 + 1]) {
flag = true;
break;
}
}
if (flag) {
puts("IMPOSSIBLE");
} else {
puts("POSSIBLE");
for (int i = 0; i < n; ++i) {
if (id[i * 2] < id[i * 2 + 1]) {
write(0, ' ');
} else {
write(1, ' ');
}
}
}
return 0;
}