Submission #286596

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Source Code Expand

#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <deque>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <ctime>
#include <iterator>
#include <bitset>
#include <numeric>
#include <list>
#include <iomanip>

#if __cplusplus >= 201103L
#include <array>
#include <tuple>
#include <initializer_list>
#include <unordered_set>
#include <unordered_map>
#include <forward_list>

#define cauto const auto&
#define ALL(v) begin(v),end(v)
#else
#define ALL(v) (v).begin(),(v).end()
#endif

using namespace std;


namespace{
typedef long long LL;
typedef pair<int,int> pii;
typedef pair<LL,LL> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<long long> vll, vLL;
typedef vector<vector<long long> > vvll, vvLL;

#define VV(T) vector<vector< T > >

template <class T>
void initvv(vector<vector<T> > &v, int a, int b, const T &t = T()){
	v.assign(a, vector<T>(b, t));
}

template <class F, class T>
void convert(const F &f, T &t){
	stringstream ss;
	ss << f;
	ss >> t;
}


#define REP(i,n) for(int i=0;i<int(n);++i)
#define RALL(v) (v).rbegin(),(v).rend()


#define MOD 1000000007LL
#define EPS 1e-8


VV(int) G;
vint hs;

int dfs(int u, int prv){
	int ret = 0;
	for(int v : G[u]){
		if(v == prv){ continue; }
		ret += max(dfs(v, u) + 1, 0);
	}
	if(!hs[u] && !ret){
		ret = -1010101010;
	}
	return ret;
}

void mainmain(){
	int n, x;
	cin >> n >> x;
	--x;
	hs.resize(n);
	for(int i = 0; i < n; ++i){
		cin >> hs[i];
	}
	G.resize(n);
	for(int i = 0; i < n - 1; ++i){
		int a, b;
		cin >> a >> b;
		G[a - 1].push_back(b - 1);
		G[b - 1].push_back(a - 1);
	}
	
	int res = max(dfs(x, -1), 0) * 2;
	printf("%d\n", res);
}



}
int main() try{
	mainmain();
}
catch(...){}

Submission Info

Judge Result