Submission #252910

#	Time	Username	Problem	Language	Result	Execution time	Memory
252910		Blagojce	Tug of War (BOI15_tug)	C++11	41 / 100	3070 ms	59648 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;

set <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);
	}
}
bool dp[6000][6000];
int suma, sumb;
int deg[mxn];
void pruning(){
	queue<int> Q;
	fr(i, 0, n){
		if(deg[i] == 1) Q.push(i);
	}
	while(!Q.empty()){
		int c = Q.front();
		Q.pop();
		
		int ed = *g[c].begin();
		int nx = trans(c, ed);
		g[c].erase(ed);
		g[nx].erase(ed);
		
		--deg[c];
		--deg[nx];
		
		used[ed] = 2;
		
		if(deg[nx] == 1) Q.push(nx);
		
		if(c == l[ed]){
			suma += s[ed];
		}
		else{
			sumb += s[ed];
		}
	}
}


void solve(){

	cin >> n>> k;
	n *= 2;
	bool sub3 = true;
	fr(i, 0, n){
		cin >> l[i] >> r[i] >> s[i];
		r[i] += n/2;
		--l[i], --r[i];
		if(s[i] != 1) sub3 = false;
		
		deg[l[i]]++;
		deg[r[i]]++;
		
		g[l[i]].insert(i);
		g[r[i]].insert(i);
	}
	pruning();
	
	vector<pii> diff;
	fr(i, 0, n){
		if(used[i] == 2) continue;
		
		vis[l[i]] = 1;
		used[i] = 1;
		OK = true;
		
		tempa = s[i], tempb = 0;
		dfs(l[i], 1);
		bool ok1 = OK;
		int val1 = tempa-tempb;
		
		vis[r[i]] = 2;
		used[i] = 2;
		OK = true;
		tempa = 0, tempb = s[i];
		dfs(r[i], 2);
		bool ok2 = OK;
		int val2 = tempa-tempb;
		
		diff.pb({val1, val2});
		
		if(!ok1 && !ok2){	
			cout<<"NO"<<endl;
			return;	
		}
	}
	if(sub3){
		cout<<"YES"<<endl;
		return;
	}
	
	int base = 50*n;
	
	int len = diff.size();	
	memset(dp, false, sizeof(dp));
	dp[0][base + suma - sumb] = true;
	
	fr(i, 1, len+1){
		fr(pr, 0, 100*n){
			if(!dp[i-1][pr]) continue;
			dp[i][pr+diff[i-1].st] = true;
			dp[i][pr+diff[i-1].nd] = true;
		}
	}
	
	fr(i, 0, k+1){
		if(dp[len][base+i]||dp[len][base-i]){
			cout<<"YES"<<endl;
			return;
		}
	}
cout<<"NO"<<endl;
	
}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	solve();
	
}

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