Submission #534947

#	Time	Username	Problem	Language	Result	Execution time	Memory
534947		leinad2	Star Trek (CEOI20_startrek)	C++17	38 / 100	105 ms	38972 KiB

startrek

#include<bits/stdc++.h>
using namespace std;
int n, i, j, k, a, b, d, A[2][2], mod=1e9+7;
vector<int>adj[100010], w[100010];
long long ans;
struct st
{
    int a, b;
};
st f(st a, st b)
{
    a.a=max(a.a, b.b);
    a.b=min(a.b, b.a);
    return a;
}
st dp[100010], dp2[100010][2][2], dp3[100010];
vector<st>pre[100010], suf[100010];
void dfs(int v, int par)
{
    dp[v].a=0;dp[v].b=1;
    for(auto p:adj[v])
    {
        if(p==par)continue;
        w[v].push_back(p);
        dfs(p, v);
        dp[v]=f(dp[v], dp[p]);
    }
}
void dfs2(int v, int par)
{
    int cnt=0;
    for(auto p:w[v])
    {
        for(int i=0;i<2;i++)for(int j=0;j<2;j++)
        {
            st a={0, 1};
            if(cnt>0)a=f(a, pre[v][cnt-1]);
            if(cnt+1<w[v].size())a=f(a, suf[v][cnt+1]);
            a=f(a, {i, j});
            dp2[p][i][j]=dp2[v][a.a][a.b];
        }
        cnt++;
        dfs2(p, v);
    }
}
void dfs3(int v, int par)
{
    int cnt=0;
    for(auto p:w[v])
    {
        st a={0, 1};
        if(v!=1)a=f(a, dp3[v]);
        if(cnt>0)a=f(a, pre[v][cnt-1]);
        if(cnt+1<w[v].size())a=f(a, suf[v][cnt+1]);
        dp3[p]=a;
        cnt++;
        dfs3(p, v);
    }
}
main()
{
    scanf("%d %d", &n, &d);
    for(i=0;++i<n;)
    {
        scanf("%d %d", &a, &b);
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    dfs(1, 0);
    for(i=0;i++<n;)if(w[i].size())
    {
        st a={0, 1};
        pre[i].resize(w[i].size());
        suf[i].resize(w[i].size());
        for(j=0;j<w[i].size();j++)
        {
            a=f(a, dp[w[i][j]]);
            pre[i][j]={a.b, a.a};
        }
        a={0, 1};
        for(j=(int)w[i].size()-1;j>=0;j--)
        {
            a=f(a, dp[w[i][j]]);
            suf[i][j]={a.b, a.a};
        }
    }
    dp2[1][0][0]={0, 0};
    dp2[1][0][1]={0, 1};
    dp2[1][1][0]={1, 0};
    dp2[1][1][1]={1, 1};
    dfs2(1, 0);
    dfs3(1, 0);
    for(i=0;i++<n;)
    {
        st a={0, 1};
        for(auto p:w[i])
        {
            a=f(a, dp[p]);
        }
        if(i!=1)a=f(a, dp3[i]);
        dp3[i]=a;
    }
    for(i=0;i++<n;)A[dp3[i].a][dp3[i].b]++;
    for(i=0;i++<n;)
    {
        for(int j=0;j<2;j++)for(int k=0;k<2;k++)
        {
            st a=dp[i];
            a=f(a, {j, k});
            ans+=dp2[i][a.a][a.b].a*A[j][k];
        }
    }
    cout<<ans%mod;
}

Compilation message (stderr)

startrek.cpp: In function 'void dfs2(int, int)':
startrek.cpp:38:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |             if(cnt+1<w[v].size())a=f(a, suf[v][cnt+1]);
      |                ~~~~~^~~~~~~~~~~~
startrek.cpp: In function 'void dfs3(int, int)':
startrek.cpp:54:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   54 |         if(cnt+1<w[v].size())a=f(a, suf[v][cnt+1]);
      |            ~~~~~^~~~~~~~~~~~
startrek.cpp: At global scope:
startrek.cpp:60:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   60 | main()
      | ^~~~
startrek.cpp: In function 'int main()':
startrek.cpp:75:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   75 |         for(j=0;j<w[i].size();j++)
      |                 ~^~~~~~~~~~~~
startrek.cpp:62:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   62 |     scanf("%d %d", &n, &d);
      |     ~~~~~^~~~~~~~~~~~~~~~~
startrek.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);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 8 / 8
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15