Submission #4711264

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Source Code Expand

#include <iostream>
#include <cstdio>
#define IsDigit(x) ((x) >= '0' && (x) <= '9')
using namespace std;

int n, pos;
int last[200001], parity[200001], cross_edge[100001];
struct Edge{
	int y, prev, dir;
}edge[600000];


int Read(void)
{
	int c, ret(0);
	bool sign(false);
	
	c = getchar();
	while (!IsDigit(c) && c != '-')
		c = getchar();
	c == '-' && (sign = true, c = getchar());
	do
		ret = ret * 10 + c - '0';
	while ((c = getchar()) && IsDigit(c));
	return sign ? -ret : ret;
}


inline void AddBiEdge(const int x, const int y)
{
	edge[pos].y = y;
	edge[pos].prev = last[x];
	last[x] = pos++;
	edge[pos].y = x;
	edge[pos].prev = last[y];
	last[y] = pos++;
	return;
}


int main()
{
	int ance, root_A, root_B;
	
	n = Read();
	pos = 2;
	for (int i = 1; i <= n; ++i) {
		ance = Read();
		if (ance == -1)
			root_A = i;
		else {
			AddBiEdge(i, ance);
			++parity[ance];
		}
	}
	for (int i = 1; i <= n; ++i) {
		ance = Read();
		if (ance == -1)
			root_B = n + i;
		else {
			AddBiEdge(n + i, n + ance);
			++parity[n + ance];
		}
	}
	for (int i = 1; i <= n; ++i)
		if ((parity[i] & 1) ^ (parity[n + i] & 1)) {
			printf("IMPOSSIBLE\n");
			return 0;
		}
		else
			if (~parity[i] & 1) {
				AddBiEdge(i, n + i);
				cross_edge[i] = pos - 2;
			}
	AddBiEdge(root_A, root_B);
	for (int src = 1; src <= n << 1; ++src) {
		while (last[src] && edge[last[src]].dir)
			last[src] = edge[last[src]].prev;
		if (!last[src])
			continue;
		register int curr = src;
		do {
			while (edge[last[curr]].dir)
				last[curr] = edge[last[curr]].prev;
			edge[last[curr]].dir = 1;
			edge[last[curr] ^ 1].dir = 2;
			curr = edge[last[curr]].y;
		}
		while (curr != src);
	}
	printf("POSSIBLE\n");
	for (int i = 1; i <= n; ++i)
		if (cross_edge[i])
			printf(edge[cross_edge[i]].dir == 1 ? "-1 " : "1 ");
		else
			printf("0 ");
	printf("\n");
	return 0;
}

Submission Info

Judge Result