Submission #99791

#	Time	Username	Problem	Language	Result	Execution time	Memory
99791		Retro3014	Beads and wires (APIO14_beads)	C++17	100 / 100	257 ms	25740 KiB

beads

#include <bits/stdc++.h>

#define pb push_back
#define all(v) ((v).begin(), (v).end())
#define sortv(v) sort(all(v))
#define sz(v) ((int)(v).size())
#define uniqv(v) (v).erase(unique(all(v)), (v).end())
#define umax(a, b) (a)=max((a), (b))
#define umin(a, b) (a)=min((a), (b))
#define FOR(i,a,b) for(int i = (a); i <= (b); i++)
#define rep(i,n) FOR(i,1,n)
#define rep0(i,n) FOR(i,0,(int)(n)-1)
#define FI first
#define SE second
#define INF 2000000000
#define INFLL 1000000000000000000LL


using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, ll> pil;

const int MAX_N = 200000;

int N;
vector<pil> gp[MAX_N+1];
int p[MAX_N+1];
int c[MAX_N+1];
ll dp[MAX_N+1][4];


void dfs(int x){
	for(auto i : gp[x]){
		if(i.first==p[x])	continue;
		p[i.first] = x;
		c[i.first] = i.second;
		dfs(i.first);
	}
	for(auto i : gp[x])	{
		if(i.first==p[x])	continue;
		dp[x][0] += max(dp[i.first][0], dp[i.first][2]);
	}
	ll mx = -INF;
	dp[x][1] = dp[x][2] = dp[x][3] = -INF;
	for(auto i : gp[x]){
		if(i.first==p[x])	continue;
		mx = max(mx, max(dp[i.first][1], dp[i.first][3]) - max(dp[i.first][0], dp[i.first][2]));
	}
	dp[x][1] = dp[x][0] + mx;
	ll mx1 = -INF, mx2 = -INF;
	for(auto i : gp[x]){
		if(i.first==p[x])	continue;
		dp[x][1] = max(dp[x][1], dp[x][0] + mx1 + dp[i.first][1] + i.second - max(dp[i.first][0], dp[i.first][2]));
		dp[x][1] = max(dp[x][1], dp[x][0] + mx2 + dp[i.first][0] + i.second - max(dp[i.first][0], dp[i.first][2]));
		dp[x][1] = max(dp[x][1], dp[x][0] + mx1 + dp[i.first][0] + i.second - max(dp[i.first][0], dp[i.first][2]));
		mx1 = max(mx1, dp[i.first][0] + i.second - max(dp[i.first][0], dp[i.first][2]));
		mx2 = max(mx2, dp[i.first][1] + i.second - max(dp[i.first][0], dp[i.first][2]));
	}
	for(auto i : gp[x]){
		if(i.first==p[x])	continue;
		dp[x][2] = max(dp[x][2], dp[x][0] + dp[i.first][0] + i.second - max(dp[i.first][0], dp[i.first][2]) + c[x]);
	}
	for(auto i : gp[x]){
		if(i.first==p[x])	continue;
		dp[x][3] = max(dp[x][3], c[x] + dp[x][0] + dp[i.first][1] + i.second - max(dp[i.first][0], dp[i.first][2]));
	}
	/*cout<<x<<endl;
	for(int i=0; i<4; i++){
		cout<<dp[x][i]<<' ';
	}cout<<endl;*/
}

int main(){
	scanf("%d", &N);
	for(int i=0; i<N-1; i++){
		int x, y; ll z;
		scanf("%d%d%lld", &x, &y, &z);
		gp[x].push_back({y, z}); gp[y].push_back({x, z});
	}
	dfs(1);
	cout<<max(dp[1][0], dp[1][1]);
	return 0;
}

Compilation message (stderr)

beads.cpp: In function 'int main()':
beads.cpp:76:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
  ~~~~~^~~~~~~~~~
beads.cpp:79:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%lld", &x, &y, &z);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43