Submission #252806

#	Time	Username	Problem	Language	Result	Execution time	Memory
252806		Blagojce	Tug of War (BOI15_tug)	C++11	0 / 100	10 ms	12160 KiB

tug

#include <bits/stdc++.h> 
#define fr(i, n, m) for(int i = (n); i < (m); i ++)
#define pb push_back
#define st first
#define nd second
#define pq priority_queue
#define all(x) begin(x), end(x)
#include <time.h>
#include <cmath>

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;

const int i_inf = 1e9;
const ll inf = 1e18;
const ll mod = 1000000007;
const ld eps = 1e-13;
const ld pi  = 3.14159265359;
 
mt19937 _rand(time(NULL));
clock_t timer = clock();
const int mxn = 5e5;

int l[mxn], r[mxn], s[mxn];
int n, k;

vector<int> g[mxn];
int used[mxn];
int vis[mxn];

//int tempa, tempb;
int trans(int u, int ed){
	if(u == l[ed]){
		//tempb += s[ed];
		return r[ed];
	}
	else{
		//tempa += s[ed];
		return l[ed];
	}
}

bool OK;
void dfs(int u, int flag){
	
	for(auto e : g[u]){
		if(used[e] == flag) continue;
		used[e] = flag;
		int nx = trans(u, e); 
		if(vis[nx] == flag){
			OK = false;
		}
		vis[nx] = flag;
		dfs(nx, flag);
	}
}


void solve(){

	cin >> n>> k;
	n *= 2;
	fr(i, 0, n){
		cin >> l[i] >> r[i] >> s[i];
		r[i] += n/2;
		--l[i], --r[i];
	}
	int suma = 0;
	int sumb = 0;
	int deg[n];
	memset(deg, 0, sizeof(deg));
	fr(i, 0, n){
		deg[l[i]]++;
		deg[r[i]]++;
	}
	fr(i, 0, n){
		if(deg[l[i]] == 1 && deg[r[i]] == 1){
			cout<<"NO"<<endl;
			return;
		}
		if(deg[l[i]] == 1){
			suma += s[i];
		}
		else if(deg[r[i]] == 1){
			sumb += s[i];
		}
		else{
			g[l[i]].pb(i);
			g[r[i]].pb(i);
		}
	}
	//vector<pii> diff;
	fr(i, 0, n){
		if(used[i] == 2) continue;
		
		
		vis[l[i]] = 1;
		used[i] = 1;
		OK = true;
		dfs(l[i], 1);
		bool ok1 = OK;
		
	
		
		vis[r[i]] = 2;
		used[i] = 2;
		OK = true;
		dfs(r[i], 2);
		bool ok2 = OK;
		if(!ok1 && !ok2){
			
			cout<<"NO"<<endl;
			return;
			
		}
		
		/*
		tempa = 0, tempb = 0;
		OK = true;
		dfs(l[i], 1);
		int F = tempa-tempb;
		if(!OK){
			F = -i_inf;
		}
		
		tempa = 0, tempb = 0;
		OK = true;
		dfs(r[i], 2);
		int S = tempa-tempb;
		if(!OK){
			S = -i_inf;
		}
		
		if(F == -i_inf && S == -i_inf){
			cout<<i<<"NO"<<endl;
			return;
		}
		diff.pb({F, S});*/
	}
	cout<<"YES"<<endl;
	
}
int main(){
	freopen("tug3b.in", "r", stdin);
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	solve();
	
}

Compilation message (stderr)

tug.cpp: In function 'int main()':
tug.cpp:146:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("tug3b.in", "r", stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 30
• Subtask 3: 0 / 23
• Subtask 4: 0 / 29