Submission #244495

#	Time	Username	Problem	Language	Result	Execution time	Memory
244495		dwsc	Potemkin cycle (CEOI15_indcyc)	C++14	60 / 100	48 ms	2804 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;
int n,m;
vector<int> adj[1010];
int depth[1010],p[1010];
int relabel[1010];
int counter;
int visited[1010];
int rmap[1010];
void dfs(int u,int pa){
    visited[u] = 1;
    //cout << u << pa << "hi\n";
    for (int i = 0; i < adj[u].size(); i++){
        int v = adj[u][i];
        if (!visited[v]){
            p[v] = u;
            depth[v] = depth[u]+1;
            visited[v] = 1;
            dfs(v,u);
        }
    }
    relabel[u] = ++counter;
    rmap[relabel[u]] = u;
}
vector<int> lowestjump[1010];
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 0; i < m; i++){
        int x,y;
        cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    for (int i = 1; i <= n; i++){
        if (!visited[i]){
            depth[i] = 1;
            p[i] = -1;
            dfs(i,-1);
        }
    }
    vector<ii> backedges;
    for (int i = 1; i <= n; i++){
        if (p[i] != -1) assert(relabel[p[i]] > relabel[i]);
        for (int j = 0; j < adj[i].size(); j++){
            int ni = adj[i][j];
            if (p[ni] == i || p[i] == ni) continue;
            if (depth[i] < depth[ni]) continue;
            lowestjump[i].push_back(relabel[ni]);
            if (depth[i]-depth[ni] >= 3) backedges.push_back(ii(i,ni));
        }
        lowestjump[i].push_back(relabel[p[i]]);
        sort(lowestjump[i].begin(),lowestjump[i].end());
    }
    for (int i = 0; i < backedges.size(); i++){
        int minjump = 1e9;
        int start = backedges[i].first, fin = backedges[i].second;
        //cout << start << " " << fin << "\n";
        int counter = 1;
        int cur = start;
        vector<int> temp;
        temp.push_back(cur);
        while (relabel[cur] < relabel[fin]){
            int relabelval = *(upper_bound(lowestjump[cur].begin(),lowestjump[cur].end(),relabel[fin])-1);
            if (cur == start) relabelval = *(lower_bound(lowestjump[cur].begin(),lowestjump[cur].end(),relabel[fin])-1);
            int pos = rmap[relabelval];
            cur = pos;
            temp.push_back(cur);
            //start++;
        }
        if (cur != fin || temp.size() < 4) continue;
        for (int j = 0; j < temp.size(); j++) cout <<temp[j] << " ";
        return 0;
    }
    cout << "no";
    return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'void dfs(int, int)':
indcyc.cpp:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < adj[u].size(); i++){
                     ~~^~~~~~~~~~~~~~~
indcyc.cpp: In function 'int main()':
indcyc.cpp:47:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < adj[i].size(); j++){
                         ~~^~~~~~~~~~~~~~~
indcyc.cpp:57:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < backedges.size(); i++){
                     ~~^~~~~~~~~~~~~~~~~~
indcyc.cpp:74:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < temp.size(); j++) cout <<temp[j] << " ";
                         ~~^~~~~~~~~~~~~
indcyc.cpp:58:13: warning: unused variable 'minjump' [-Wunused-variable]
         int minjump = 1e9;
             ^~~~~~~
indcyc.cpp:61:13: warning: unused variable 'counter' [-Wunused-variable]
         int counter = 1;
             ^~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 10 / 10
• Subtask 7: 0 / 10
• Subtask 8: 10 / 10
• Subtask 9: 0 / 10
• Subtask 10: 10 / 10