Submission #244447

#	Time	Username	Problem	Language	Result	Execution time	Memory
244447		SomeoneUnknown	Potemkin cycle (CEOI15_indcyc)	C++14	30 / 100	43 ms	1280 KiB

indcyc

#include <bits/stdc++.h>
using namespace std;

vector<int> adjlist[1001];

bool isadj(int a, int b){
    int lo = -1;
    int hi = adjlist[a].size();
    while(hi-lo > 1){
        int mid = (hi+lo)/2;
        if(adjlist[a][mid] == b) return true;
        if(adjlist[a][mid] < b){
            lo = mid;
        }else{
            hi = mid;
        }
    }
    return false;
}
int main(){
    int n, r;
    scanf("%d %d", &n, &r);
    int ved[n+1];
    for(int i = 1; i <= n; ++i) ved[i] = 0; //unvisited
    for(int i = 0; i < r; ++i){
        int a, b;
        scanf("%d %d", &a, &b);
        adjlist[a].push_back(b);
        adjlist[b].push_back(a);
    }
    for(int i = 1; i <= n; ++i){
        sort(adjlist[i].begin(), adjlist[i].end());
    }
    for(int i = 1; i <= n; ++i){
        if(ved[i] != 0) continue;
        ved[i] = -1; //root
        queue<int> tovisit;
        tovisit.push(i);
        while(!tovisit.empty()){
            int ving = tovisit.front();
            //printf("ving = %d\n", ving);
            tovisit.pop();
            for(int j = 0; j < adjlist[ving].size(); ++j){
                int nghbr = adjlist[ving][j];
                if(ved[nghbr] == 0){
                    ved[nghbr] = ving;
                    tovisit.push(nghbr);
                }else if(ved[ving] != nghbr && !isadj(ved[nghbr], ving)){
                    stack<int> s;
                    queue<int> e;
                    //s.push(ving);
                    //e.push(nghbr);
                    int last;
                    int sptr = ving;
                    int eptr = nghbr;
                    while(sptr != eptr){
                        e.push(eptr);
                        //printf("e: %d\n", eptr);
                        last = eptr;
                        eptr = ved[eptr];

                        if(sptr == eptr) break;
                        s.push(sptr);
                        //printf("s: %d\n", sptr);
                        sptr = ved[sptr];
                    }
                    //return 5; //doesnt reach
                    bool djoint = true;
                    for(int k = 0; k < adjlist[s.top()].size(); k++){
                        if(adjlist[s.top()][k] == last) djoint = false;
                    }
                    if(djoint)
                        printf("%d ", sptr);
                    while(!s.empty()){
                        printf("%d ", s.top());
                        s.pop();
                    }
                    while(!e.empty()){
                        printf("%d ", e.front());
                        e.pop();
                    }
                    return 0;
                }
            }
        }
    }
    printf("no");
}
/*
5 5
1 2
2 3
2 4
3 5
4 5
*/

Compilation message (stderr)

indcyc.cpp: In function 'int main()':
indcyc.cpp:43:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int j = 0; j < adjlist[ving].size(); ++j){
                            ~~^~~~~~~~~~~~~~~~~~~~~~
indcyc.cpp:69:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     for(int k = 0; k < adjlist[s.top()].size(); k++){
                                    ~~^~~~~~~~~~~~~~~~~~~~~~~~~
indcyc.cpp:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &r);
     ~~~~~^~~~~~~~~~~~~~~~~
indcyc.cpp:27:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~~
indcyc.cpp:70:25: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized]
                         if(adjlist[s.top()][k] == last) djoint = false;
                         ^~

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