Submission #650679

#	Time	Username	Problem	Language	Result	Execution time	Memory
650679		Spade1	Islands (IOI08_islands)	C++14	64 / 100	344 ms	131072 KiB

islands

#include<bits/stdc++.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define ll long long
#define ld long double
#define st first
#define nd second
#define pb push_back
#define INF INT_MAX
using namespace std;

const int N = 1e6 + 10;

vector<pair<int, pll>> adj[N];
bool vis[N];

int cycle;

vector<pll> v;
ll dp[N], qs[N], ans, cur;

pll dfs2(int i, int prt1, int prt2) {
    ll mx_w = 0, mx = i;
    for (auto [j, w] : adj[i]) {
        if (j == prt1 || j == prt2) continue;
        pll ret = dfs2(j, i, 0);
        if (ret.nd + w.nd > mx_w) {
            mx_w = ret.nd + w.nd;
            mx = ret.st;
        }
    }
    return {mx, mx_w};
}

int dfs(int i, int ed, int prt) {
    if (vis[i]) {
        cycle = prt;
        return i;
    }
    vis[i] = 1;
    int ret = 0, K, W;
    for (auto [j, w] : adj[i]) {
        if (j == prt && ed == w.st) continue;
        if (ret != 0 && vis[j]) continue;
        int k = dfs(j, w.st, i);
        if (k) {
            ret = k;
            K = j;
            W = w.nd;
        }
    }
    if (ret == i) {
        auto [val, w] = dfs2(i, K, cycle);
        v.pb({w, W});
        return 0;
    }
    else if (ret) {
        auto [val, w] = dfs2(i, prt, K);
        v.pb({w, W});
    }
    return ret;
}

void solve() {
    int n; cin >> n;
    for (int i = 1; i <= n; ++i) {
        int b, w; cin >> b >> w;
        adj[i].pb({b ,{i, w}});
        adj[b].pb({i, {i, w}});
    }

    for (int i = 1; i <= n; ++i) {
        if (vis[i]) continue;
        dfs(i, 0, 0);
        int m = v.size();
        for (int j = 0; j <= m+1; ++j) qs[j] = 0, dp[j] = 0;
        for (int j = 1; j <= m; ++j) {
            qs[j] = qs[j-1] + v[j-1].nd;
            dp[j] = qs[j] + v[j-1].st;
        }
        for (int j = m-1; j > 0; --j) dp[j] = max(dp[j], dp[j+1]);
        for (int j = 1; j < m; ++j) {
            cur = max(cur, v[j-1].st - qs[j] + dp[j+1]);
        }
        for (int j = 0; j <= m+1; ++j) dp[j] = 0;
        for (int j = m; j >= 1; --j) {
            dp[j] = qs[j] + v[j-1].st;
        }
        for (int j = 2; j <= m; ++j) dp[j] = max(dp[j], dp[j-1]);
        for (int j = 2; j <= m; ++j) {
            cur = max(cur, qs[m] + v[j-1].st - qs[j] + dp[j-1]);
        }
        ans += cur;
        v.clear();
        cur = 0, cycle = 0;
    }
    cout << ans << '\n';
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(NULL);
    int t = 1;
//    cin >> t;
    while (t--) {
        solve();
    }
}

Compilation message (stderr)

islands.cpp: In function 'std::pair<long long int, long long int> dfs2(int, int, int)':
islands.cpp:24:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   24 |     for (auto [j, w] : adj[i]) {
      |               ^
islands.cpp: In function 'int dfs(int, int, int)':
islands.cpp:42:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   42 |     for (auto [j, w] : adj[i]) {
      |               ^
islands.cpp:53:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   53 |         auto [val, w] = dfs2(i, K, cycle);
      |              ^
islands.cpp:58:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   58 |         auto [val, w] = dfs2(i, prt, K);
      |              ^
islands.cpp:53:41: warning: 'K' may be used uninitialized in this function [-Wmaybe-uninitialized]
   53 |         auto [val, w] = dfs2(i, K, cycle);
      |                                         ^

• Subtask 1: 27 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 0 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10