Submission #424774

#	Time	Username	Problem	Language	Result	Execution time	Memory
424774		zoooma13	The Xana coup (BOI21_xanadu)	C++14	0 / 100	128 ms	24600 KiB

xanadu

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

#define MAX_N 100005

vector <int> state;
vector <vector <int>> adj;

int dp[2][2][MAX_N];
int dfs(int u ,bool st ,bool sp ,int p = -1){
    if(adj[u].size() == 1 && p != -1)
        return (state[u]^sp) == st? st : MAX_N;
    auto&ret = dp[st][sp][u];
    if(~ret)
        return ret;
    ret = MAX_N;
    vector <pair<int ,int>> chld;
    for(int&v : adj[u]) if(v != p)
        chld.push_back({dfs(v ,0 ,st ,u) ,dfs(v ,1 ,st ,u)});
    sort(chld.begin() ,chld.end() ,[](auto&i ,auto&j){
        return i.second-i.first < j.second-j.first;
    });
    int64_t tot = 0;
    for(int i = 0; i < chld.size(); i++)
        tot += chld[i].first;
    int j = 0;
    if((state[u]^sp) != st)
        tot += chld[j].second - chld[j].first ,j++;
    ret = min((int64_t)ret ,tot);
    while(j < chld.size()){
        tot += chld[j].second - chld[j].first ,j++;
        if(j == chld.size()) break;
        tot += chld[j].second - chld[j].first ,j++;
        ret = min((int64_t)ret ,tot);
    }
    return ret + st;
}

int main()
{
    int n;
    scanf("%d",&n);
    adj.resize(n+1);
    state.resize(n+1);
    for(int a ,b ,i = 1; i < n; i++){
        scanf("%d%d",&a,&b);
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    for(int i = 1; i <= n; i++)
        scanf("%d",&state[i]);

    memset(dp ,-1 ,sizeof dp);
    int ans = min(dfs(1 ,0 ,0) ,dfs(1 ,1 ,0));
    printf(ans >= MAX_N? "impossible\n" : "%d\n",ans);
}

Compilation message (stderr)

xanadu.cpp: In function 'int dfs(int, bool, bool, int)':
xanadu.cpp:24:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |     for(int i = 0; i < chld.size(); i++)
      |                    ~~^~~~~~~~~~~~~
xanadu.cpp:30:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |     while(j < chld.size()){
      |           ~~^~~~~~~~~~~~~
xanadu.cpp:32:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |         if(j == chld.size()) break;
      |            ~~^~~~~~~~~~~~~~
xanadu.cpp: In function 'int main()':
xanadu.cpp:42:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
xanadu.cpp:46:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |         scanf("%d%d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~
xanadu.cpp:51:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         scanf("%d",&state[i]);
      |         ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 0 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30