Submission #532855

#	Time	Username	Problem	Language	Result	Execution time	Memory
532855		79brue	Newspapers (CEOI21_newspapers)	C++14	100 / 100	98 ms	508 KiB

newspapers

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

namespace Naive{
    int n, m;
    int dissappear[25];
    vector<int> link[25];

    int movemove(int source){
        int rv = 0;
        for(int i=0; i<n; i++){
            if(source & (1<<i)){
                for(int j=0; j<(int)link[i].size(); j++){
                    rv |= (1<<link[i][j]);
                }
            }
        }
    //    printf("movemove %d is %d\n", source, rv);
        return rv;
    }

    void bfs(){
        int temp;
        map<int, bool> visited;
        map<int, pair<int, int> > parent;
        queue<int> que;
        stack<int> ans;
        que.push((1<<n)-1);
        visited[(1<<n)-1] = true;
        while(1){
            if(que.empty()){
                printf("NO\n");
                return;
            }
            temp = que.front();
    //        printf("bfs %d\n", temp);
            que.pop();
            if(!temp) break;
            for(int i=0; i<n; i++){
                if(!(temp & (1<<i))) continue;
                int tmp_val = movemove(temp - (1<<i));
                if(!visited[tmp_val]){
                    que.push(tmp_val);
                    parent[tmp_val] = make_pair(temp, i);
    //                printf("parent of %d is %d(deleted %d)\n", tmp_val, temp, i);
                    visited[tmp_val] = true;
                }
            }
        }
        int cnt = 0, mark = 0;
        while(mark != (1<<n)-1){
            cnt++;
            ans.push(parent[mark].second);
            mark = parent[mark].first;
        }
        printf("YES\n%d\n", cnt);
        for(int i=0; i<cnt; i++){
            printf("%d ", ans.top()+1);
            ans.pop();
        }
        puts("");
    }

    void main(){
        int s, e;
        if(m!=n-1){
            puts("NO");
            exit(0);
        }
        for(int i=0; i<n; i++) link[i].clear();
        for(int i=1; i<=m; i++){
            scanf("%d %d", &s, &e);
            s--, e--;
            link[s].push_back(e), link[e].push_back(s);
        }
        for(int i=0; i<n; i++){
            dissappear[i] = 0;
            for(int j=0; j<(int)link[i].size(); j++){
                if((int)link[link[i][j]].size() == 1) dissappear[i] |= (1<<link[i][j]);
            }
        }
        bfs();
    }
}

int n, m;
vector<int> link[1002];
int maxDepth, maxIdx;
int p[1002];

int dfs(int x, int par = -1, int depth = 0){
    vector<int> vec (1, 0);
    p[x] = par;
    if(maxDepth < depth) maxIdx = x, maxDepth = depth;
    for(auto y: link[x]){
        if(y==par) continue;
        int tmp = dfs(y, x, depth+1);
        vec.push_back(tmp+1);
    }

    sort(vec.rbegin(), vec.rend());
    if(par == -1){
        if(vec.size() >= 3 && vec[2] >= 3){
            puts("NO");
            exit(0);
        }
    }
    return vec[0];
}

int depth[1002];
vector<int> line;
vector<vector<int> > lineChild;
vector<vector<int> > lineChildCnt;
vector<int> ans;

int main(){
    scanf("%d %d", &n, &m);
    if(n<=10){
        Naive::n = n;
        Naive::m = m;
        Naive::main();
        return 0;
    }

    if(m!=n-1){
        puts("NO");
        return 0;
    }

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

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

    maxDepth = 0; dfs(1);
    int A = maxIdx;
    maxDepth = 0; dfs(A);
    int B = maxIdx;

    {
        int x = B;
        while(x != -1){
            line.push_back(x);
            depth[x] = 1;
            x = p[x];
        }
        reverse(line.begin(), line.end());
    }
    lineChild.resize(line.size());
    lineChildCnt.resize(line.size());

    for(int i=1; i<=n; i++){
        if(depth[i] == 1) continue;
        if(depth[p[i]] == 1){
            depth[i] = 2;
            int idx = find(line.begin(), line.end(), p[i]) - line.begin();
            lineChild[idx].push_back(i);
            lineChildCnt[idx].push_back(0);
        }
    }
    for(int i=1; i<=n; i++){
        if(depth[i] == 1 || depth[i] == 2) continue;
        if(depth[p[i]] == 2){
            depth[i] = 3;
            int idx = find(line.begin(), line.end(), p[p[i]]) - line.begin();
            lineChildCnt[idx][find(lineChild[idx].begin(), lineChild[idx].end(), p[i]) - lineChild[idx].begin()]++;
        }
    }

    for(int i=1; i<(int)line.size()-1; i++){
        ans.push_back(line[i]);
        for(int j=0; j<(int)lineChild[i].size(); j++){
            if(lineChildCnt[i][j]) ans.push_back(lineChild[i][j]), ans.push_back(line[i]);
        }
    }
    if(count(ans.begin(), ans.end(), ans.back()) >= 2) ans.pop_back();
    if(count(ans.begin(), ans.end(), ans[0]) >= 2) ans.erase(ans.begin());

    printf("YES\n%d\n", (int)ans.size()*2);
    for(auto x: ans) printf("%d ", x);
    if((int)ans.size() % 2 == 0){
        reverse(ans.begin(), ans.end());
    }
    for(auto x: ans) printf("%d ", x);
}

Compilation message (stderr)

newspapers.cpp: In function 'void Naive::main()':
newspapers.cpp:75:18: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   75 |             scanf("%d %d", &s, &e);
      |             ~~~~~^~~~~~~~~~~~~~~~~
newspapers.cpp: In function 'int main()':
newspapers.cpp:121:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |     scanf("%d %d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~~
newspapers.cpp:136:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  136 |         scanf("%d %d", &x, &y);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 8 / 8
• Subtask 3: 80 / 80