Submission #36939

#	Time	Username	Problem	Language	Result	Execution time	Memory
36939		aome	Potemkin cycle (CEOI15_indcyc)	C++14	100 / 100	223 ms	8100 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;
 
const int N = 1005;
 
int n, m;
int nxt[N][N];
int par[N];
bool E[N][N];
bool finish[N][N];
vector<int> go;
 
void cal(int x, int y) {
	vector<int > vx, vy;
	while (par[x] != x) vx.push_back(x), x = par[x];
	vx.push_back(x);
	while (par[y] != y) vy.push_back(y), y = par[y];
	reverse(vy.begin(), vy.end());
	for (auto i : vy) vx.push_back(i);
	for (auto i : vx) cout << i << ' ';
}

void trace() {
	int sz = go.size();
	for (auto i : go) par[i] = 0;
	queue<int> qu;
	par[go[0]] = go[0], qu.push(go[0]); 
	while (qu.size()) {
		int u = qu.front(); qu.pop();
		for (auto v : go) {
			if (!E[u][v]) continue;
			if (!par[v]) {
				par[v] = u, qu.push(v);
			}
			else if (par[u] != v) {
				cal(u, v); exit(0);
			}
		}
	}
}
 
void dfs(int x, int y) {
	for (int i = 1; i <= n; ++i) {
		if (!E[y][i] || E[x][i]) continue;
		if (nxt[y][i] < 0 || finish[y][i]) continue;
		if (nxt[y][i] > 0) {
			int curx = x, cury = y;
			while (curx != y && cury != i) {
				go.push_back(cury);
				int tmp = nxt[curx][cury];
				cury = curx, curx = tmp;
			}
			go.push_back(cury), trace(); 
		}
		else nxt[y][i] = x, nxt[i][y] = -x, dfs(y, i);
	}
	finish[x][y] = finish[y][x] = 1;
}
 
int main() {
	ios::sync_with_stdio(false);
	cin >> n >> m;
	for (int i = 1; i <= m; ++i) {
		int u, v; cin >> u >> v;
		E[u][v] = E[v][u] = 1;
	}
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= n; ++j) {
			if (!E[i][j] || nxt[i][j]) continue;
			nxt[i][j] = i, nxt[j][i] = -i, E[j][i] = 0, dfs(i, j);
		}
	}
	cout << "no";
}

Compilation message (stderr)

indcyc.cpp: In function 'void trace()':
indcyc.cpp:24:6: warning: unused variable 'sz' [-Wunused-variable]
  int sz = go.size();
      ^

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10