[Link] https://www.acmicpc.net/problem/11280
IDEA
(N U M) = true <=> (!N => M) || (M => !N)
[ 1~n, -1 ~ -n ] => SCC => (a => b => c … => (-a)) => can’t be solved(When SCC includes x and -x)
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import java.util.*;
import java.io.*;
public class Main {
static BufferedReader br;
static StringBuilder sb = new StringBuilder();
static int sccIdx = 1;
static Stack<Integer> stack = new Stack<>();
static int[] parent;
static boolean[] finished;
static boolean cantSolve = false;
static Node[] nodes;
static int n;
public static void main(String[] args) throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
int[] arr = getArr();
n = arr[0];
int m = arr[1];
nodes = new Node[2 * n];
finished = new boolean[2 * n];
parent = new int[2 * n];
for(int i = 1; i <=n; i++) nodes[convert(i)] = new Node(i);
for(int i = -n; i <= -1; i++) nodes[convert(i)] = new Node(i);
for(int i = 0; i < m; i++) {
arr = getArr();
int a = arr[0], b = arr[1], bit1 = a > 0 ? 1 : -1, bit2 = b > 0 ? 1 : -1;
nodes[convert((-1) * a)].list.add(b);
nodes[convert((-1) * b)].list.add(a);
}
for(int j = 0; j < 2 * n ; j++) {
if(parent[j] == 0) scc(j);
if(cantSolve) {
print(0);
return;
}
}
print(1);
}
//0 ~ (n-1) : 1 ~(n) || n ~ (2n - 1): -1 ~ -n
static int convert(int idx) { return idx > 0 ? idx - 1 : n - 1 - idx; }
static int rev(int idx) { return idx < n ? idx + 1 : n - 1 - idx; }
static int scc(int idx) {
int origVal = parent[idx] = sccIdx++;
stack.push(idx);
for(int e: nodes[idx].list) {
if(parent[convert(e)] == 0) parent[idx] = Math.min(parent[idx], scc(convert(e)));
else if(finished[convert(e)] == false) parent[idx] = Math.min(parent[idx], parent[convert(e)]);
}
if(origVal == parent[idx]) {
HashSet<Integer> hs = new HashSet<>();
while(true) {
int pop = stack.pop();
int rev = rev(pop);
if(hs.contains((-1) * rev)) cantSolve = true;
hs.add(rev);
finished[pop] = true;
if(pop == idx) break;
}
}
return parent[idx];
}
static class Node {
int idx;
ArrayList<Integer> list = new ArrayList<>();
public Node(int idx) { this.idx = idx; }
}
static int toi(String s) { return Integer.parseInt(s); }
static String[] getLine() throws IOException { return br.readLine().split(" "); }
static int[] getArr() throws IOException { return Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); }
static <T> void print(T s) { System.out.print(s); }
static <T> void println(T s) { System.out.println(s); }
}