Submission #680436

#	Time	Username	Problem	Language	Result	Execution time	Memory
680436		qwerasdfzxcl	Wells (CEOI21_wells)	C++17	0 / 100	58 ms	72264 KiB

wells

#include <bits/stdc++.h>

typedef long long ll;
using namespace std;
int dist[10010][10010], vcnt, n, k;
vector<int> adj[1501500], G[1501500], st;
vector<vector<int>> path;

void dfs(int s, int pa = -1){
    st.push_back(s);
    if ((int)st.size()==k) path.push_back(st);
    dist[st[0]][s] = (int)st.size() - 1;

    for (auto &v:adj[s]) if (v!=pa){
        dfs(v, s);
    }

    st.pop_back();
}

int col[1501500];
bool simulate(int s){
    vector<int> q = {s};
    fill(col+1, col+n+1, 0);
    col[s] = 1;

    while(!q.empty()){
        int v = q.back(); q.pop_back();
        for (int i=1;i<=n;i++) if (dist[v][i]==k && !col[i]){
            col[i] = 1;
            q.push_back(i);
        }
    }

    vector<vector<int>> npath;
    for (auto &p:path){
        int cnt = 0;
        for (auto &x:p) if (col[x]) cnt++;
        if (cnt>1) return 0;

        if (cnt==0) npath.push_back(p);
    }
    swap(path, npath);
    return 1;
}

int main(){
    scanf("%d %d", &n, &k);
    for (int i=1;i<=n-1;i++){
        int x, y;
        scanf("%d %d", &x, &y);
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    for (int i=1;i<=n;i++){
        dfs(i);
    }

    for (int i=1;i<=n;i++) if (simulate(i) && path.empty()){
        printf("YES\n0\n");
        return 0;
    }
    printf("NO\n0\n");
    return 0;
}

Compilation message (stderr)

wells.cpp: In function 'int main()':
wells.cpp:48:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |     scanf("%d %d", &n, &k);
      |     ~~~~~^~~~~~~~~~~~~~~~~
wells.cpp:51:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         scanf("%d %d", &x, &y);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 30