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Submission #358465

# Submission time Handle Problem Language Result Execution time Memory
358465 2021-01-25T14:20:20 Z CaroLinda Beads and wires (APIO14_beads) C++14
100 / 100
 281 ms 29928 KB 
#include <bits/stdc++.h>

#define ll long long
#define all(x) x.begin(),x.end()
#define sz(x) (int)(x.size())

const int MAXN = 2e5+10 ;
const int inf = 1e9+7 ;

using namespace std ;

int n ;
int ans ;
int dp[MAXN][2] ;
vector< pair<int,int> > adj[MAXN] ;

void dfs(int x, int father )
{
	int edgeFather = -inf ;
	vector< pair<int,int> > children ;

	for(auto e : adj[x] ) 
	{
		if(e.first == father)
			edgeFather = e.second ;
		else 
		{
			dfs(e.first, x) ;
			children.push_back(e) ;
		}
	}

	dp[x][0] = 0;
	dp[x][1] = edgeFather ;
	int maxCte = -inf ;

	for(auto e : children )
	{
		int pos1 = dp[e.first][1] ;
		int pos2 = dp[e.first][0] ;

		dp[x][0] += max(pos1, pos2) ;
		dp[x][1] += max(pos1,pos2) ;

		maxCte = max(maxCte, -max(pos1,pos2) + e.second + pos2 ) ;

	}

	dp[x][1] += maxCte ;
	
}

void dfsSpin(int x, int father)
{

	vector< pair<int,int> > children ;

	for(auto e : adj[x] ) 
		children.push_back(e) ;

	int m = sz(children) ;
	int soma = 0 ;

	vector<int> pref(m) , suf(m) ;

	for(int i = 0 , ii = m-1 ; i < m ; i++ , ii-- )
	{
		int vert = children[i].first ;
		int edge = children[i].second ;

		soma += max( dp[vert][0] , dp[vert][1] ) ;

		pref[i] = -max(dp[vert][0] , dp[vert][1]) + edge + dp[vert][0] ;
		
		vert = children[ii].first ;
		edge = children[ii].second ;

		suf[ii] = -max(dp[vert][0] , dp[vert][1]) + edge + dp[vert][0] ;

		if(!i) continue ;

		pref[i] = max(pref[i-1], pref[i]) ;
		suf[ii] = max(suf[ii+1] , suf[ii]) ;

	}

	ans = max(ans, soma ) ;

	for(int i = 0 ; i < m ; i++ )
	{
		int vert = children[i].first ;
		int edge = children[i].second ;

		if(vert == father) continue ;

		int save0 = dp[vert][0] ;
		int save1 = dp[vert][1] ;

		int cte = -inf ;
		if(i) cte = max(cte, pref[i-1]) ;
		if(i+1 < m) cte = max(cte, suf[i+1]) ;

		dp[x][0] = soma-max(save0,save1) ;
		dp[x][1] = soma-max(save0,save1) + cte + edge ;

		dfsSpin(vert, x) ;

		dp[vert][0] = save0 ;
		dp[vert][1] = save1 ;

	}

}

int main()
{

	scanf("%d", &n ) ;

	if(n == 1)
	{
		printf("0\n") ;
		return 0 ;
	}

	for(int i = 1 , a , b , c ; i < n ; i++ )
	{
		scanf("%d%d%d", &a, &b, &c ) ;

		adj[a].push_back(make_pair(b,c)) ;
		adj[b].push_back( make_pair(a,c) ) ;

	}

	dfs(1,-1);
	dfsSpin(1,-1) ;

	printf("%d\n" , ans ) ;

}

Compilation message

beads.cpp: In function 'int main()':
beads.cpp:118:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  118 |  scanf("%d", &n ) ;
      |  ~~~~~^~~~~~~~~~~
beads.cpp:128:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  128 |   scanf("%d%d%d", &a, &b, &c ) ;
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
13.0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 4972 KB Output is correct
2 Correct 4 ms 4972 KB Output is correct
3 Correct 3 ms 4972 KB Output is correct
4 Correct 3 ms 4972 KB Output is correct
5 Correct 4 ms 4972 KB Output is correct
6 Correct 4 ms 4972 KB Output is correct
7 Correct 4 ms 4972 KB Output is correct
8 Correct 3 ms 4972 KB Output is correct
9 Correct 4 ms 4972 KB Output is correct
10 Correct 3 ms 4972 KB Output is correct
11 Correct 3 ms 4972 KB Output is correct
12 Correct 4 ms 4972 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 4972 KB Output is correct
2 Correct 4 ms 4972 KB Output is correct
3 Correct 3 ms 4972 KB Output is correct
4 Correct 3 ms 4972 KB Output is correct
5 Correct 4 ms 4972 KB Output is correct
6 Correct 4 ms 4972 KB Output is correct
7 Correct 4 ms 4972 KB Output is correct
8 Correct 3 ms 4972 KB Output is correct
9 Correct 4 ms 4972 KB Output is correct
10 Correct 3 ms 4972 KB Output is correct
11 Correct 3 ms 4972 KB Output is correct
12 Correct 4 ms 4972 KB Output is correct
13 Correct 3 ms 4972 KB Output is correct
14 Correct 3 ms 4972 KB Output is correct
15 Correct 4 ms 4972 KB Output is correct
16 Correct 4 ms 4972 KB Output is correct
17 Correct 4 ms 4972 KB Output is correct
18 Correct 4 ms 4992 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct
21 Correct 4 ms 4972 KB Output is correct
22 Correct 4 ms 5100 KB Output is correct

Subtask #3
29.0 / 29.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 4972 KB Output is correct
2 Correct 4 ms 4972 KB Output is correct
3 Correct 3 ms 4972 KB Output is correct
4 Correct 3 ms 4972 KB Output is correct
5 Correct 4 ms 4972 KB Output is correct
6 Correct 4 ms 4972 KB Output is correct
7 Correct 4 ms 4972 KB Output is correct
8 Correct 3 ms 4972 KB Output is correct
9 Correct 4 ms 4972 KB Output is correct
10 Correct 3 ms 4972 KB Output is correct
11 Correct 3 ms 4972 KB Output is correct
12 Correct 4 ms 4972 KB Output is correct
13 Correct 3 ms 4972 KB Output is correct
14 Correct 3 ms 4972 KB Output is correct
15 Correct 4 ms 4972 KB Output is correct
16 Correct 4 ms 4972 KB Output is correct
17 Correct 4 ms 4972 KB Output is correct
18 Correct 4 ms 4992 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct
21 Correct 4 ms 4972 KB Output is correct
22 Correct 4 ms 5100 KB Output is correct
23 Correct 7 ms 5484 KB Output is correct
24 Correct 7 ms 5356 KB Output is correct
25 Correct 7 ms 5356 KB Output is correct
26 Correct 13 ms 5612 KB Output is correct
27 Correct 11 ms 5612 KB Output is correct
28 Correct 9 ms 5868 KB Output is correct
29 Correct 9 ms 5740 KB Output is correct
30 Correct 9 ms 5740 KB Output is correct
31 Correct 11 ms 6636 KB Output is correct

Subtask #4
43.0 / 43.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 4972 KB Output is correct
2 Correct 4 ms 4972 KB Output is correct
3 Correct 3 ms 4972 KB Output is correct
4 Correct 3 ms 4972 KB Output is correct
5 Correct 4 ms 4972 KB Output is correct
6 Correct 4 ms 4972 KB Output is correct
7 Correct 4 ms 4972 KB Output is correct
8 Correct 3 ms 4972 KB Output is correct
9 Correct 4 ms 4972 KB Output is correct
10 Correct 3 ms 4972 KB Output is correct
11 Correct 3 ms 4972 KB Output is correct
12 Correct 4 ms 4972 KB Output is correct
13 Correct 3 ms 4972 KB Output is correct
14 Correct 3 ms 4972 KB Output is correct
15 Correct 4 ms 4972 KB Output is correct
16 Correct 4 ms 4972 KB Output is correct
17 Correct 4 ms 4972 KB Output is correct
18 Correct 4 ms 4992 KB Output is correct
19 Correct 4 ms 5100 KB Output is correct
20 Correct 4 ms 5100 KB Output is correct
21 Correct 4 ms 4972 KB Output is correct
22 Correct 4 ms 5100 KB Output is correct
23 Correct 7 ms 5484 KB Output is correct
24 Correct 7 ms 5356 KB Output is correct
25 Correct 7 ms 5356 KB Output is correct
26 Correct 13 ms 5612 KB Output is correct
27 Correct 11 ms 5612 KB Output is correct
28 Correct 9 ms 5868 KB Output is correct
29 Correct 9 ms 5740 KB Output is correct
30 Correct 9 ms 5740 KB Output is correct
31 Correct 11 ms 6636 KB Output is correct
32 Correct 44 ms 8044 KB Output is correct
33 Correct 43 ms 8044 KB Output is correct
34 Correct 42 ms 8044 KB Output is correct
35 Correct 281 ms 17644 KB Output is correct
36 Correct 267 ms 17644 KB Output is correct
37 Correct 280 ms 17644 KB Output is correct
38 Correct 182 ms 21600 KB Output is correct
39 Correct 160 ms 21348 KB Output is correct
40 Correct 179 ms 20824 KB Output is correct
41 Correct 264 ms 29928 KB Output is correct