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| #include <bits/stdc++.h>
#define Weakoying ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define int long long
#define pii pair<int, int>
#define vi vector<int>
#define vii vector<pair<int, int>>
#define pqueue priority_queue
#define pb push_back
#define F first
#define S second
#define max(a, b) (a > b ? a : b)
#define min(a, b) (a < b ? a : b)
#define cmax(a, b) a = (a > b ? a : b)
#define cmin(a, b) a = (a < b ? a : b)
#define put(x) cout << x << endl;
#define DB(x) cerr << #x << " " << x << endl
#define all(v) v.begin(), v.end()
#define stop system("pause");
#define MEM(x, n) memset(x, n, sizeof(x));
#define lowbit(x) x &(-x)
#define SZ(v) ((int)v.size())
#if !LOCAL
#define endl "\n"
#pragma GCC optimize("Ofast", "unroll-all-loops")
#endif
const int INF = 0x3f3f3f3f3f3f3f3f;
const int P = 1e9+7;
using namespace std;
#define MAXN 200005
#define MAXM 1000005
int n, m;
vector<int> G[MAXN];
int rev(int i) {
return (i + m) % (m * 2);
}
struct Tarjan {
int tt, sccId;
int dep[MAXN], low[MAXN], scc[MAXN];
int opp[MAXN];
bitset<MAXN> inSt;
stack<int> st;
void dfs(int i, int pa) {
dep[i] = low[i] = ++tt;
st.push(i);
inSt[i] = true;
for (int e: G[i]) {
if (!dep[e]) {
dfs(e, i);
cmin(low[i], low[e]);
}
else if (inSt[e]) {
cmin(low[i], dep[e]);
}
}
if (low[i] == dep[i]) {
int p;
sccId++;
do {
p = st.top();
st.pop();
inSt[p] = false;
scc[p] = sccId;
} while (p != i);
}
}
void main() {
for (int i = 0; i < 2 * m; i++) {
if (!dep[i])
dfs(i, i);
}
}
bool check() {
for (int i = 0; i < m; i++) {
if (scc[i] == scc[rev(i)])
return false;
opp[scc[i]] = scc[rev(i)];
opp[scc[rev(i)]] = scc[i];
}
return true;
}
} Tarjan;
struct Solver {
vector<int> G2[MAXN];
int in[MAXN];
int ans[MAXN];
void build() {
for (int i = 0; i < 2 * m; i++) {
for (int e: G[i]) if (Tarjan.scc[i] != Tarjan.scc[e]) {
G2[Tarjan.scc[e]].pb(Tarjan.scc[i]);
in[Tarjan.scc[i]]++;
}
}
}
void topo() {
queue<int> q;
for (int i = 1; i <= Tarjan.sccId; i++) {
if (!in[i])
q.push(i);
}
while (q.size()) {
auto now = q.front();
q.pop();
if (!ans[now]) {
ans[now] = 1;
ans[Tarjan.opp[now]] = 2;
}
for (int e: G2[now]) {
in[e]--;
if (!in[e])
q.push(e);
}
}
for (int i = 0; i < m; i++)
cout << (ans[Tarjan.scc[i]] == 1 ? "+ " : "- ");
cout << endl;
}
} Solver;
void sol() {
cin >> n >> m;
for (int i = 0; i < n; i++) {
char c1, c2;
int a1, a2;
cin >> c1 >> a1 >> c2 >> a2;
a1--, a2--;
if (c1 == '-')
a1 += m;
if (c2 == '-')
a2 += m;
G[rev(a1)].pb(a2);
G[rev(a2)].pb(a1);
}
Tarjan.main();
if (!Tarjan.check()) {
cout << "IMPOSSIBLE" << endl;
return;
}
Solver.build();
Solver.topo();
}
signed main() {
Weakoying;
int t = 1;
{
while (t--) {
sol();
}
}
return 0;
}
|