제출 #137364

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
137364		egorlifar	구슬과 끈 (APIO14_beads)	C++17	100 / 100	288 ms	23148 KiB

beads

/*
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 */
#include <iostream>
#include <complex>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <numeric>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <cmath>
#include <bitset>
#include <cassert>
#include <queue>
#include <stack>
#include <deque>
#include <random>
 
using namespace std;
template<typename T1, typename T2>inline void chkmin(T1 &x, T2 y) { if (x > y) x = y; }
template<typename T1, typename T2>inline void chkmax(T1 &x, T2 y) { if (x < y) x = y; }
#define sz(c) (int)(c).size()
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define left left224
#define right right224
#define next next224
#define rank rank224
#define prev prev224
#define y1 y1224
#define read(FILENAME) freopen((FILENAME + ".in").c_str(), "r", stdin)
#define write(FILENAME) freopen((FILENAME + ".out").c_str(), "w", stdout)
#define files(FILENAME) read(FILENAME), write(FILENAME)
#define pb push_back
#define mp make_pair
const string FILENAME = "input";
const int MAXN = 200228;


int n;
vector<pair<int, int> > g[MAXN];
int dp[MAXN][2];
int up[MAXN][2];


void dfs(int u, int pr = -1, int last = 0) {
    int sum = 0;
    int add = -1e9;
    for (auto h: g[u]) {
        if (h.first == pr) {
            continue;
        }
        dfs(h.first, u, h.second);
        sum += max(dp[h.first][0], dp[h.first][1]); 
        chkmax(add, dp[h.first][0] - max(dp[h.first][0], dp[h.first][1]) + h.second + last);
    }
    dp[u][0] = sum;
    dp[u][1] = sum + add;
} 


int ans = 0;


void calcdp(int u, int pr = -1, int last = 0) {
    chkmax(ans, max(up[u][0], up[u][1]) + dp[u][0]);
    int cnt = 0;
    int mx1 = -1e9, mx2 = -1e9;
    for (auto h: g[u]) {
        if (h.first == pr) {
            continue;
        }
        int add = dp[h.first][0] - max(dp[h.first][0], dp[h.first][1]) + h.second;
        cnt++;
        if (mx1 < add) {
            mx2 = mx1;
            mx1 = add;
        } else {
            chkmax(mx2, add);
        }
    }
    for (auto h: g[u]) {
        if (h.first == pr) {
            continue;
        }
        int add = dp[h.first][0] - max(dp[h.first][0], dp[h.first][1]) + h.second;
        int sum = dp[u][0] - max(dp[h.first][0], dp[h.first][1]);
        if (u) {
            up[h.first][1] = up[u][0] + last + h.second + sum;
        }
        if (cnt > 1) {
            int val = (add == mx1 ? mx2: mx1);
            chkmax(up[h.first][1], h.second + sum + val + max(up[u][0], up[u][1]));
        }
        up[h.first][0] = max(up[u][0], up[u][1]) + sum;
        calcdp(h.first, u, h.second);
    }
}
 

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
   // read(FILENAME); 
    cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        a--, b--;
        g[a].pb({b, c});
        g[b].pb({a, c});
    }
    dfs(0);
    calcdp(0);
    cout << ans << endl;
}   

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