Submission #261682

#	Time	Username	Problem	Language	Result	Execution time	Memory
261682		ant101	Tug of War (BOI15_tug)	C++14	23 / 100	13 ms	3328 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 = 60005;
 
int n, k;
int l[mxn], r[mxn], s[mxn];
 
vector<int> g[mxn];
 
int deg[mxn];
 
int used[mxn];
int vis[mxn];
 
 
int nxt(int u, int ed){
	return l[ed]^r[ed]^u;
}
void build(){
	fr(i, 0, n){
		l[i] = l[i]-1;
		r[i] = r[i]-1+n/2;
	}
	fr(i, 0, n){
		g[l[i]].pb(i);
		g[r[i]].pb(i);
		++deg[l[i]];
		++deg[r[i]];
	}
}
void remove(int ed){
	used[ed] = 2;
	--deg[l[ed]], --deg[r[ed]];	
}  
void update(int &sa, int &sb, int u, int ed){
	if(u == l[ed]) sa += s[ed];
	else sb += s[ed];
}
 
int find_one(int u){
	for(auto e : g[u]){
		if(used[e] == 2) continue;
		return e;
	}
}
int suma, sumb;
void pruning(){
	queue<int> Q;
	fr(i, 0, n) if(deg[i] == 1) Q.push(i);
	while(!Q.empty()){
		int u = Q.front();
		Q.pop();
		int ed = find_one(u);
		remove(ed);
		update(suma, sumb, u, ed);
		if(deg[nxt(u, ed)] == 1) Q.push(nxt(u,ed));
	}
}
void dfs(int u, int flag, int &sa, int &sb){
	for(auto e : g[u]){
		if(used[e] == flag) continue;
		if(vis[nxt(u, e)] == flag){
			cout<<"NO"<<endl;
			exit(0);
		}
		used[e] = flag, vis[nxt(u, e)] = flag;
		update(sa, sb, nxt(u, e), e);
		dfs(nxt(u, e), flag, sa, sb);
	}
}
pii direct_edge(int ed){
	int sa1 = s[ed], sb1 = 0;
	used[ed] = 1, vis[l[ed]] = 1;
	dfs(l[ed], 1, sa1, sb1);
 
	int sa2 = 0, sb2 = s[ed];
	used[ed] = 2, vis[r[ed]] = 2;
	dfs(r[ed], 2, sa2, sb2);
		
	return {sa1-sb1, sa2-sb2};
}
 
bitset<20*mxn> dp;
 
void solve(){
	cin >> n >> k;
	n <<= 1;
	bool sub3 = true;
	fr(i, 0, n){
		cin >> l[i] >> r[i] >> s[i];
		if(s[i] != 1) sub3 = false;
	}
	build();
	pruning();
	
	vector<pii> v;
	
	fr(i, 0, n){
		if(used[i] == 2) continue;	
		v.pb(direct_edge(i));
	}
	if(sub3){
		cout<<"YES"<<endl;
		return;
	}
	
	int m = v.size();
	
	dp[20*(n>>1)+suma-sumb] = 1;
	
	fr(i, 0, m){
		
		if(v[i].st > 0 && v[i].nd > 0) dp = (dp<<v[i].st)|(dp<<v[i].nd);
		else if(v[i].st > 0 && v[i].nd < 0) dp = (dp<<v[i].st)|(dp>>(-v[i].nd));
		else if(v[i].st < 0 && v[i].nd > 0) dp = (dp>>(-v[i].st))|(dp<<v[i].nd);
		else dp = (dp>>(-v[i].st))|(dp>>(-v[i].nd));
	}
	
	fr(i, 0, k+1){
		if(dp[20*(n>>1)+i]||dp[20*(n>>1)-i]){
			cout<<"YES"<<endl;
			return;
		}
	}
	cout<<"NO"<<endl;
}
 
 
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	solve();
}

Compilation message (stderr)

tug.cpp: In function 'int find_one(int)':
tug.cpp:66:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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