/*
_____
.' '.
/ 0 0 \
| ^ |
| \ / |
\ '---' /
'._____.'
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
struct chash
{
int operator()(int x) const
{
x ^= (x >> 20) ^ (x >> 12);
return x ^ (x >> 7) ^ (x >> 4);
}
};
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using hashtable = gp_hash_table<T, U, chash>;
random_device(rd);
mt19937 rng(rd());
template<class T>
void readi(T &x)
{
T input = 0;
bool negative = false;
char c = ' ';
while (c < '-')
{
c = getchar();
}
if (c == '-')
{
negative = true;
c = getchar();
}
while (c >= '0')
{
input = input * 10 + (c - '0');
c = getchar();
}
if (negative)
{
input = -input;
}
x = input;
}
template<class T>
void printi(T output)
{
if (output == 0)
{
putchar('0');
return;
}
if (output < 0)
{
putchar('-');
output = -output;
}
int aout[20];
int ilen = 0;
while(output)
{
aout[ilen] = ((output % 10));
output /= 10;
ilen++;
}
for (int i = ilen - 1; i >= 0; i--)
{
putchar(aout[i] + '0');
}
return;
}
template<class T>
void ckmin(T &a, T b)
{
a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
a = max(a, b);
}
template<class T, class U>
T nmod(T &x, U mod)
{
if (x >= mod) x -= mod;
}
template<class T>
T gcd(T a, T b)
{
return (b ? gcd(b, a % b) : a);
}
template<class T>
T randomize(T mod)
{
return (uniform_int_distribution<T>(0, mod - 1))(rng);
}
#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define debug(x) cerr << #x << " = " << x << endl;
const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-10;
#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 200013
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;
int N;
vector<pii> edge[MAXN];
int parent[MAXN], dup[MAXN];
vector<int> ord;
int res[2][2];
int dp[MAXN][2][2];
void dfs(int u)
{
for (pii p : edge[u])
{
int d = p.fi, v = p.se;
if (v == parent[u])
{
continue;
}
parent[v] = u;
dup[v] = d;
dfs(v);
}
ord.PB(u);
}
void init()
{
res[0][0] = 0; res[0][1] = 0; res[1][0] = 0; res[1][1] = 0;
}
void assign(int u)
{
ckmax(dp[u][0][0], res[0][0]);
ckmax(dp[u][0][1], res[0][1]);
ckmax(dp[u][1][0], res[1][0]);
ckmax(dp[u][1][1], res[1][1]);
}
int32_t main()
{
ios_base::sync_with_stdio(0);
// cout << fixed << setprecision(10);
// cerr << fixed << setprecision(10);
// freopen ("file.in", "r", stdin);
// freopen ("file.out", "w", stdout);
cin >> N;
for (int i = 1; i < N; i++)
{
int u, v, d;
cin >> u >> v >> d;
u--; v--;
edge[u].PB({d, v});
edge[v].PB({d, u});
}
parent[0] = N; dup[0] = -INF;
dfs(0);
for (int i = 0; i < N; i++)
{
int u = ord[i];
// cerr << u << endl;
//dp[vertex][taking only guy to parent][have u gotten a cut]
// res[1][0] = dup[u] + sum over all v of dp[v][0][0]
// res[1][1] = dup[u] + sum over all v of dp[v][0][1]
res[1][0] = dup[u];
res[1][1] = dup[u];
for (pii p : edge[u])
{
int v = p.se;
if (v == parent[u]) continue;
res[1][0] += dp[v][0][0];
res[1][1] += dp[v][0][1];
}
assign(u); init();
//if u dont take u, then:
//res[0][0] = sum over all v of dp[v][0][0]
//res[0][1] = sum over all v of dp[v][0][1]
//if u take two chidlren of u: it's always ok
//res[0][1] = sum over all v except 2 of dp[v][0][1] plus the two dp[v][1]][1]
int mx0 = -INF, mx1 = -INF;
for (pii p : edge[u])
{
int v = p.se;
if (v == parent[u]) continue;
res[0][1] += dp[v][0][1];
int dif = dp[v][1][1] - dp[v][0][1];
if (dif > mx0)
{
mx1 = mx0; mx0 = dif;
}
else if (dif > mx1)
{
mx1 = dif;
}
}
res[0][1] += mx0; res[0][1] += mx1;
res[1][1] = res[0][1] + dup[u];
assign(u); init();
mx0 = -INF; mx1 = -INF;
//if u take one child of u and v
//res[0][0] = sum over all v except 1 of dp[v][0][0] plus dp[v][1][0] + dup[u]
//res[0][1] = sum over all v except 1 of dp[v][0][0] plus dp[v][1][1] + dup[u]
res[0][0] = dup[u];
res[0][1] = dup[u];
for (pii p : edge[u])
{
int v = p.se;
if (v == parent[u]) continue;
res[0][0] += dp[v][0][0];
res[0][1] += dp[v][0][0];
ckmax(mx0, dp[v][1][0] - dp[v][0][0]);
ckmax(mx1, dp[v][1][1] - dp[v][0][0]);
}
res[0][0] += mx0; res[0][1] += mx1;
assign(u); init();
ckmax(dp[u][1][1], dp[u][1][0]);
ckmax(dp[u][0][1], dp[u][0][0]);
// cerr << "vertex " << u << ' ' << dp[u][0][0] << ' ' << dp[u][0][1] << ' ' << dp[u][1][0] << ' ' << dp[u][1][1] << endl;
}
cout << dp[0][0][1] << '\n';
//possibilities: u took 1 or u havent
//ur subtree is stupid or its not
//the path between anytwo endpoints must go through a third point?
// cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 2 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 3 |
Incorrect |
6 ms |
5120 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 2 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 3 |
Incorrect |
6 ms |
5120 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 2 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 3 |
Incorrect |
6 ms |
5120 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 2 |
Correct |
6 ms |
4992 KB |
Output is correct |
| 3 |
Incorrect |
6 ms |
5120 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
