Submission #1882251

---

Source Code Expand

#include <cstdio>
#include <vector>
#include <algorithm>
int p[200001], N, d[200001], q[200001], D, vi[200001], sg[200001], cir[200001], L, w1[200001], w2[200001], w[200001];
std::vector < int > E[200001];
bool NiroBC(int start)
{
	w[1] = start;
	for (int i = 2; i <= L; i++)
		w[i] = w[i - 1] == w1[i] ? w2[i] : w1[i];
	return w[1] == (w[L] == w1[1] ? w2[1] : w1[1]);
}
int main()
{
	scanf("%d", &N);
	for (int i = 1; i <= N; i++)
	{
		scanf("%d", p + i);
		E[p[i]].push_back(i);
		d[p[i]]++;
	}
	for (int i = 1; i <= N; i++)
		if (!d[i])
			q[++D] = i;
	while (D)
	{
		int u = q[D--];
		for (int v : E[u])
			vi[sg[v]] = 1;
		while (vi[sg[u]])
			sg[u]++;
		for (int v : E[u])
			vi[sg[v]] = 0;
		if (!--d[p[u]])
			q[++D] = p[u];
	}
	for (int i = std::find(d + 1, d + N + 1, 1) - d; d[i] == 1; i = p[i])
		d[cir[++L] = i] = -1;
	for (int i = 1; i <= L; i++)
	{
		int u = cir[i];
		for (int v : E[u])
			if (d[v] != -1)
				vi[sg[v]] = 1;
		while (vi[w1[i]])
			w1[i]++;
		w2[i] = w1[i] + 1;
		while (vi[w2[i]])
			w2[i]++;
		for (int v : E[u])
			if (d[v] != -1)
				vi[sg[v]] = 0;
	}
	puts(NiroBC(w1[1]) || NiroBC(w2[1]) ? "POSSIBLE" : "IMPOSSIBLE");
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:15:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
                 ^
./Main.cpp:18:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", p + i);
                     ^

Judge Result