Submission #337315

#	Time	Username	Problem	Language	Result	Execution time	Memory
337315		Giselus	Railway (BOI17_railway)	C++14	100 / 100	177 ms	24556 KiB

railway

#include<cstdio>
#include<algorithm>
#include<vector>
#define S 100007
using namespace std;
 
vector < vector < int > > L;
pair < int, int > E[S];
int num[S];
int R[S][20];
pair < int, int > t[S];
int dp[S];
bool ta[S];
int poz[S];
 
int pom = 0;
void DFS(int x, int p){
    poz[x] = poz[p]+1;
    pom++;
    num[x] = pom;
    for(int i = 1; i <= 19; i++){
        R[x][i] = R[R[x][i-1]][i-1];
    }
    for(int i = 0; i < L[x].size(); i++){
        if(L[x][i] != p){
            R[L[x][i]][0] = x;
            DFS(L[x][i],x);
        }
    }
}
 
void DFS2(int x, int p){
    for(int i = 0 ; i < L[x].size();i++){
        if(L[x][i] != p){
            DFS2(L[x][i],x);
            dp[x] += dp[L[x][i]];
        }
    }
}
 
int LCA(int x, int y){
    if(poz[y] > poz[x])
        swap(x,y);
    for(int i = 19;i >= 0;i--){
        if(poz[R[x][i]] >= poz[y])
            x = R[x][i];
    }
    if(x == y)
        return x;
    for(int i = 19; i >= 0;i--){
        if(R[x][i] != R[y][i]){
            x = R[x][i];
            y = R[y][i];
        }
    }
    return R[x][0];
}
 
int main(void){
 
    int n,m,a,b,c,d,x,k,q;
    scanf("%d %d %d",&n,&m,&k);
    L.resize(n+7);
    for(int i = 1; i <= n-1; i++){
        scanf("%d %d",&a,&b);
        E[i] = {a,b};
        L[a].push_back(b);
        L[b].push_back(a);
    }
    R[1][0] = 1;
    DFS(1,0);
    while(m--){
        scanf("%d",&q);
        for(int i = 0; i < q; i++){
            scanf("%d",&x);
            t[i] = {num[x],x};
        }
        sort(t,t+q);
        for(int i = 0 ; i < q;i++){
            int lca = LCA(t[i].second,t[(i+1)%q].second);
            dp[t[i].second]++;
            dp[t[(i+1)%q].second]++;
            dp[lca]-=2;
        }
    }
    DFS2(1,0);
    int odp = 0;
    for(int i = 1; i <= n-1;i++){
        if(num[E[i].first] > num[E[i].second])
            swap(E[i].first,E[i].second);
        if(dp[E[i].second] >= 2*k){
            odp++;
            ta[i] = 1;
        }
    }
    printf("%d\n",odp);
    for(int i = 1; i <= n-1;i++){
        if(ta[i])
            printf("%d ",i);
    }
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'void DFS(int, int)':
railway.cpp:24:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |     for(int i = 0; i < L[x].size(); i++){
      |                    ~~^~~~~~~~~~~~~
railway.cpp: In function 'void DFS2(int, int)':
railway.cpp:33:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |     for(int i = 0 ; i < L[x].size();i++){
      |                     ~~^~~~~~~~~~~~~
railway.cpp: In function 'int main()':
railway.cpp:61:17: warning: unused variable 'c' [-Wunused-variable]
   61 |     int n,m,a,b,c,d,x,k,q;
      |                 ^
railway.cpp:61:19: warning: unused variable 'd' [-Wunused-variable]
   61 |     int n,m,a,b,c,d,x,k,q;
      |                   ^
railway.cpp:62:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   62 |     scanf("%d %d %d",&n,&m,&k);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~
railway.cpp:65:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   65 |         scanf("%d %d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~~
railway.cpp:73:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   73 |         scanf("%d",&q);
      |         ~~~~~^~~~~~~~~
railway.cpp:75:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   75 |             scanf("%d",&x);
      |             ~~~~~^~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25