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답안 #379589

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
379589 2021-03-18T17:43:13 Z SavicS Islands (IOI08_islands) C++14
70 / 100
 546 ms 131076 KB 
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>

#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ff(i,a,b) for(int i=a;i<=b;i++)
#define fb(i,b,a) for(int i=b;i>=a;i--)

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,ll> pii;
const int maxn = 2000005;
const int inf = 1e9 + 5;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

int n;

vector<pii> g[maxn];

int nxt[maxn];
ll cost[maxn];

int krug_sta = 0;
int krug_end = 0;

int par[maxn];
int visited[maxn];
void dfs1(int v, int p){
	par[v] = p;
	visited[v] = 1;
	for(auto c : g[v]){
		int u = c.fi;
		ll w = c.se;
		if(u == p && !(nxt[p] == v && nxt[v] == p))continue;
		if(!visited[u])dfs1(u, v);
		else{
			if(visited[u] == 1){
				krug_sta = u;
				krug_end = v;
			}
		}
	}
	visited[v] = 2;
}

ll dia = 0;
bool was[maxn];
ll dfs2(int v, ll duz){
	was[v] = 1;
	ll best = duz;
	for(auto c : g[v]){
		int u = c.fi;
		ll w = c.se;
		if(!was[u]){
			ll dist = dfs2(u, duz + w);
			dia = max(dia, dist + best - 2 * duz);
			best = max(best, dist);
		}
	}		
	return best;
}

ll rez = 0;
ll pref[maxn];
ll sta[maxn];
void Solve(int x){
	dia = 0;
	dfs1(x, 0);
	
	vector<int> cycle;
	for(int i = krug_end;i != krug_sta; i = par[i]){
		cycle.pb(i);	
	}
	cycle.pb(krug_sta);
	
	vector<pii> krug;
	ff(i,1,sz(cycle) - 1){
		int a = cycle[i - 1];
		int b = cycle[i];
		ll w = (nxt[a] == b ? cost[a] : cost[b]);
		krug.pb({a, w});		
	}
	ll w = (nxt[cycle.back()] == cycle[0] ? cost[cycle.back()] : cost[cycle[0]]);
	krug.pb({cycle.back(), w});
	
	for(auto c : krug)was[c.fi] = 1;
	ff(i,0,sz(krug) - 1)sta[i] = dfs2(krug[i].fi, 0);
	
	int len = sz(krug);
	pref[0] = 0;
	ff(i,0,len - 1)pref[i + 1] = pref[i] + krug[i].se;
	
	ll zbir = pref[len];
	ll mn = -sta[0];
	ll mx = sta[0];
	ll najv = 0;
	ff(i,1,len - 1){
		najv = max(najv, pref[i] + sta[i] - mn);
		najv = max(najv, zbir + sta[i] - pref[i] + mx);
		mn = min(mn, pref[i] - sta[i]);
		mx = max(mx, pref[i] + sta[i]);
	}
	rez += max(najv, dia);
}

int main()
{
    ios::sync_with_stdio(false);
    cout.tie(nullptr);
    cin.tie(nullptr);
	cin >> n;
	ff(i,1,n){
		int a;
		ll b;
		cin >> a >> b;
		g[i].pb({a, b});
		g[a].pb({i, b});
		nxt[i] = a;
		cost[i] = b;
	}
	ff(i,1,n){
		if(!visited[i]){
			Solve(i);
		}
	}
	cout << rez << endl;
    return 0;
}
/**

3
1 1
3 2
2 3

7
3 8
7 2
4 2
1 4
1 9
3 4
2 3 


// probati bojenje sahovski ili slicno

**/

Compilation message

islands.cpp: In function 'void dfs1(int, int)':
islands.cpp:44:6: warning: unused variable 'w' [-Wunused-variable]
   44 |   ll w = c.se;
      |      ^

Subtask #1
33.0 / 33.0

# 결과 실행 시간 메모리 Grader output
1 Correct 32 ms 47340 KB Output is correct
2 Correct 35 ms 47340 KB Output is correct
3 Correct 32 ms 47468 KB Output is correct
4 Correct 35 ms 47340 KB Output is correct
5 Correct 32 ms 47340 KB Output is correct
6 Correct 32 ms 47340 KB Output is correct
7 Correct 32 ms 47340 KB Output is correct
8 Correct 33 ms 47340 KB Output is correct
9 Correct 32 ms 47340 KB Output is correct
10 Correct 32 ms 47360 KB Output is correct
11 Correct 32 ms 47352 KB Output is correct

Subtask #2
3.0 / 3.0

# 결과 실행 시간 메모리 Grader output
1 Correct 33 ms 47468 KB Output is correct
2 Correct 36 ms 47596 KB Output is correct

Subtask #3
4.0 / 4.0

# 결과 실행 시간 메모리 Grader output
1 Correct 36 ms 47468 KB Output is correct
2 Correct 38 ms 47852 KB Output is correct

Subtask #4
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 39 ms 48768 KB Output is correct
2 Correct 50 ms 51628 KB Output is correct
3 Correct 42 ms 48876 KB Output is correct
4 Correct 42 ms 48108 KB Output is correct

Subtask #5
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 56 ms 53092 KB Output is correct
2 Correct 70 ms 56624 KB Output is correct

Subtask #6
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 115 ms 63716 KB Output is correct
2 Correct 125 ms 72452 KB Output is correct
3 Correct 155 ms 80860 KB Output is correct

Subtask #7
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 177 ms 77296 KB Output is correct
2 Correct 229 ms 103612 KB Output is correct
3 Correct 254 ms 117588 KB Output is correct
4 Runtime error 298 ms 131076 KB Execution killed with signal 9

Subtask #8
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 353 ms 114868 KB Output is correct
2 Runtime error 546 ms 131072 KB Execution killed with signal 9
3 Halted 0 ms 0 KB -

Subtask #9
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Runtime error 371 ms 131076 KB Execution killed with signal 9
2 Halted 0 ms 0 KB -