#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int MAXN = 1e5+7;
const long long INF = 1e9+7;
long long dp[MAXN][3][3];
bool t[MAXN], visited[MAXN];
vector<long long> g[MAXN];
long long n,a,b,c,d;
void DFS(int x){
visited[x]=1;
if(t[x]){
dp[x][1][0]=1;
dp[x][0][1]=0;
}
else{
dp[x][1][1]=1;
dp[x][0][0]=0;
}
for(int i=0;i<g[x].size();i++){
if(visited[g[x][i]]==1) continue;
int s=g[x][i];
DFS(s);
a=dp[x][0][0], b=dp[x][0][1], c=dp[x][1][0], d=dp[x][1][1];
dp[x][0][0]=min(a+dp[s][0][0], b+dp[s][1][0]);
dp[x][0][1]=min(b+dp[s][0][0], a+dp[s][1][0]);
dp[x][1][0]=min(c+dp[s][0][1], d+dp[s][1][1]);
dp[x][1][1]=min(d+dp[s][0][1], c+dp[s][1][1]);
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin>>n;
for(int i=1;i<n;i++){
cin>>a>>b;
g[a].push_back(b);
g[b].push_back(a);
}
for(int i=1;i<=n;i++) cin>>t[i];
for(int i=1;i<=n;i++){
dp[i][0][0]=INF;
dp[i][1][0]=INF;
dp[i][0][1]=INF;
dp[i][1][1]=INF;
}
DFS(1,0);
if(dp[1][1][0]>n and dp[1][0][0]>n) cout<<"impossible\n";
else cout<<min(dp[1][1][0], dp[1][0][0])<<'\n';
return 0;
}
Compilation message
xanadu.cpp: In function 'void DFS(int)':
xanadu.cpp:20:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
20 | for(int i=0;i<g[x].size();i++){
| ~^~~~~~~~~~~~
xanadu.cpp: In function 'int main()':
xanadu.cpp:46:9: error: too many arguments to function 'void DFS(int)'
46 | DFS(1,0);
| ^
xanadu.cpp:10:6: note: declared here
10 | void DFS(int x){
| ^~~
