Submission #246551

#	Time	Username	Problem	Language	Result	Execution time	Memory
246551		dantoh000	Potemkin cycle (CEOI15_indcyc)	C++14	50 / 100	290 ms	4856 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;
int n,m;
int id[1005][1005];
int A[1005];
int B[1005];
int vis[100005];
vector<int> ans;
int cycle;
bool dfs(int a, int b){

    vis[id[a][b]] = 2;
    for (int c = 1; c <= n; c++){
        if (c != a && id[b][c] && !id[a][c]){
            if (vis[id[b][c]] == 2){
                cycle = b;
                ans.push_back(b);
                ans.push_back(a);
                return true;
            }
            else if (dfs(b,c)){
                ans.push_back(a);
                if (id[a][cycle]){
                    //for (auto x : ans) printf("%d ",x);
                    for (int x = 0; x < ans.size(); x++){
                        for (int y = x+2; y < ans.size(); y++){
                            if (id[ans[x]][ans[y]] && (x != 0 && y != ans.size()-1)){ ///xxx illegal operation
                                //printf("%d -> %d illegal \n",ans[x],ans[y]);
                                ///delete everything in it (N * N is ok)
                                ans.erase(ans.begin()+x, ans.begin()+y+1);
                                y = x+1; ///restart check
                            }
                        }
                    }
                    if (ans.size() > 3){
                        for (auto x : ans) printf("%d ",x);
                        exit(0);
                    }
                }
                return true;
            }

        }
    }
    vis[id[a][b]] = 1;
    return false;
}
int main(){
    scanf("%d%d",&n,&m);
    for (int i = 1; i <= m; i++){
        scanf("%d%d",&A[i],&B[i]);
        id[B[i]][A[i]] = id[A[i]][B[i]] = i;
    }
    for (int i = 1; i <= m; i++){
        if (vis[i] == 0) {
            dfs(A[i],B[i]);
        }
    }

    printf("no");
}

Compilation message (stderr)

indcyc.cpp: In function 'bool dfs(int, int)':
indcyc.cpp:25:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     for (int x = 0; x < ans.size(); x++){
                                     ~~^~~~~~~~~~~~
indcyc.cpp:26:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                         for (int y = x+2; y < ans.size(); y++){
                                           ~~^~~~~~~~~~~~
indcyc.cpp:27:68: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                             if (id[ans[x]][ans[y]] && (x != 0 && y != ans.size()-1)){ ///xxx illegal operation
                                                                  ~~^~~~~~~~~~~~~~~
indcyc.cpp: In function 'int main()':
indcyc.cpp:49:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
indcyc.cpp:51:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&A[i],&B[i]);
         ~~~~~^~~~~~~~~~~~~~~~~~~~

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