Submission #526142

#	Time	Username	Problem	Language	Result	Execution time	Memory
526142		mjhmjh1104	Mountains and Valleys (CCO20_day1problem3)	C++17	21 / 25	7116 ms	430540 KiB

Main

#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <set>
#include <tuple>
#include <cstdio>
#include <vector>
#include <utility>
#include <iterator>
#include <algorithm>
using namespace std;

struct Item {
    int posde;
    int negde;
    int ans;
    Item (): posde((int)-1e9), negde((int)-1e9), ans((int)-1e9) {}
    Item (int posde, int negde, int ans): posde(posde), negde(negde), ans(ans) {}
} sp_split[19][500006];

int n, m;
vector<int> tree[500006], child[500006];
vector<tuple<int, int, int>> adj;
int depth[500006], sp[19][500006], sp_dist[19][500006];
multiset<int> lt_depth[500006], lt_dist[500006];
int max_depth[500006], rev_max_depth[500006], dist[500006], rev_dist[500006];
int prev_dist[500006], prev_depth[500006][2];

int query_sp_half(int A, int x) {
    int ret = prev_depth[x][0] - depth[x];
    if (A == x) return ret;
    for (int t = 18; t >= 0; t--) if (sp[t][x] != -1 && depth[sp[t][x]] > depth[A]) {
        ret = max(ret, sp_split[t][x].negde);
        x = sp[t][x];
    }
    return max(ret, sp_split[0][x].negde);
}

int query_sp_res(int A, int x) {
    if (A == x) return (int)-1e9;
    Item ret = { prev_depth[x][0] + depth[x], prev_depth[x][0] - depth[x], (int)-1e9 };
    for (int t = 18; t >= 0; t--) if (sp[t][x] != -1 && depth[sp[t][x]] > depth[A]) {
        ret.ans = max({ sp_split[t][x].ans, ret.ans, sp_split[t][x].posde + ret.negde });
        ret.posde = max(sp_split[t][x].posde, ret.posde);
        ret.negde = max(sp_split[t][x].negde, ret.negde);
        x = sp[t][x];
    }
    return max({ sp_split[0][x].ans, ret.ans, sp_split[0][x].posde + ret.negde });
}

int dfs_dist(int x) {
    max_depth[x] = 0;
    dist[x] = 0;
    int mx0 = (int)-1e9, mx1 = (int)-1e9;
    for (auto &i: child[x]) {
        int t = dfs_dist(i) + 1;
        max_depth[x] = max(max_depth[x], t);
        if (t > mx0) mx1 = mx0, mx0 = t;
        else if (t > mx1) mx1 = t;
        dist[x] = max(dist[x], dist[i]);
    }
    dist[x] = max(dist[x], mx0 + max(mx1, 0));
    return max_depth[x];
}

void dfs_rev_dist(int x) {
    lt_depth[x].insert(rev_max_depth[x]);
    lt_dist[x].insert(rev_dist[x]);
    for (auto &i: child[x]) {
        lt_depth[x].insert(max_depth[i] + 1);
        lt_dist[x].insert(dist[i]);
    }
    for (auto &i: child[x]) {
        lt_depth[x].erase(lt_depth[x].find(max_depth[i] + 1));
        lt_dist[x].erase(lt_dist[x].find(dist[i]));
        if (!lt_dist[x].empty()) rev_dist[i] = *lt_dist[x].rbegin();
        if (!lt_depth[x].empty()) rev_dist[i] = max(rev_dist[i], rev_max_depth[i] = *lt_depth[x].rbegin() + 1);
        if ((int)lt_depth[x].size() > 1) rev_dist[i] = max(rev_dist[i], *lt_depth[x].rbegin() + *prev(prev(lt_depth[x].end())));
        lt_depth[x].insert(max_depth[i] + 1);
        lt_dist[x].insert(dist[i]);
    }
    lt_depth[x].erase(lt_depth[x].find(rev_max_depth[x]));
    lt_dist[x].erase(lt_dist[x].find(rev_dist[x]));
    for (auto &i: child[x]) dfs_rev_dist(i);
}


void dfs_f_dist(int x) {
    for (auto &i: child[x]) {
        lt_dist[x].erase(lt_dist[x].find(dist[i]));
        sp_dist[0][i] = (lt_dist[x].empty() ? 0 : *lt_dist[x].rbegin());
        lt_dist[x].insert(dist[i]);
    }
    for (auto &i: child[x]) dfs_f_dist(i);
}

void dfs_edge(int x) {
    for (auto &i: child[x]) {
        lt_depth[x].erase(lt_depth[x].find(max_depth[i] + 1));
        if ((int)lt_depth[x].size() > 1) sp_dist[0][i] = max(sp_dist[0][i], *lt_depth[x].rbegin() + *prev(prev(lt_depth[x].end())));
        else if (!lt_depth[x].empty()) sp_dist[0][i] = max(sp_dist[0][i], *lt_depth[x].rbegin());
        int V = (lt_depth[x].empty() ? 0 : *lt_depth[x].rbegin());
        sp_split[0][i].posde = V + depth[x];
        sp_split[0][i].negde = V - depth[x];
        lt_depth[x].insert(max_depth[i] + 1);
    }
    for (auto &i: child[x]) dfs_edge(i);
}

void dfs_child(int x, int prev = -1) {
    sp[0][x] = prev;
    for (auto &i: tree[x]) if (i != prev) {
        depth[i] = depth[x] + 1;
        child[x].push_back(i);
        dfs_child(i, x);
    }
}

int A, B;

int lca(int u, int v) {
    bool sw = false;
    if (depth[u] < depth[v]) swap(u, v), sw = true;
    int diff = depth[u] - depth[v];
    for (int t = 18; t >= 0; t--) if (diff >= 1 << t) {
        diff -= 1 << t;
        u = sp[t][u];
    }
    if (u == v) return u;
    for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && sp[t][v] != -1 && sp[t][u] != sp[t][v]) {
        u = sp[t][u];
        v = sp[t][v];
    }
    A = u, B = v;
    if (sw) swap(A, B);
    return sp[0][u];
}

int pr(int x, int y) {
    for (int t = 18; t >= 0; t--) if (y >= 1 << t) {
        y -= 1 << t;
        x = sp[t][x];
    }
    return x;
}

int query_sp_dist(int u, int v, int l, int A, int B) {
    int ret = 0;
    if (u != l) {
        ret = max(prev_depth[u][1], prev_dist[u]);
        u = sp[0][u];
    }
    if (v != l) {
        ret = max(prev_depth[v][1], prev_dist[v]);
        v = sp[0][v];
    }
    for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && depth[sp[t][u]] > depth[l]) {
        ret = max(ret, sp_dist[t][u]);
        u = sp[t][u];
    }
    for (int t = 18; t >= 0; t--) if (sp[t][v] != -1 && depth[sp[t][v]] > depth[l]) {
        ret = max(ret, sp_dist[t][v]);
        v = sp[t][v];
    }
    if (A != -1) lt_dist[l].erase(lt_dist[l].find(dist[A]));
    if (B != -1) lt_dist[l].erase(lt_dist[l].find(dist[B]));
    ret = max(ret, lt_dist[l].empty() ? 0 : *lt_dist[l].rbegin());
    if (A != -1) lt_dist[l].insert(dist[A]);
    if (B != -1) lt_dist[l].insert(dist[B]);
    if (A != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[A] + 1));
    if (B != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[B] + 1));
    if (!lt_depth[l].empty()) ret = max(ret, *lt_depth[l].rbegin() + rev_max_depth[l]);
    else ret = max(ret, rev_max_depth[l]);
    if ((int)lt_depth[l].size() > 1) ret = max(ret, *lt_depth[l].rbegin() + *prev(prev(lt_depth[l].end())));
    if (A != -1) lt_depth[l].insert(max_depth[A] + 1);
    if (B != -1) lt_depth[l].insert(max_depth[B] + 1);
    return ret;
}

int main() {
    scanf("%d%d", &n, &m);
    while (m--) {
        int x, y, w;
        scanf("%d%d%d", &x, &y, &w);
        if (w == 1) {
            tree[x].push_back(y);
            tree[y].push_back(x);
        } else adj.push_back({ x, y, w });
    }
    dfs_child(0);
    dfs_dist(0);
    dfs_rev_dist(0);
    for (int i = 0; i < n; i++) {
        prev_dist[i] = (lt_dist[i].empty() ? (int)-1e9 : *lt_dist[i].rbegin());
        prev_depth[i][0] = (lt_depth[i].empty() ? (int)-1e9 : *lt_depth[i].rbegin());
        prev_depth[i][1] = ((int)lt_depth[i].size() < 2 ? (int)-1e9 : *lt_depth[i].rbegin() + *prev(prev(lt_depth[i].end())));
    }
    dfs_f_dist(0);
    dfs_edge(0);
    for (int t = 1; t < 19; t++) for (int i = 0; i < n; i++) {
        if (sp[t - 1][i] == -1) {
            sp[t][i] = -1;
            sp_dist[t][i] = sp_dist[t - 1][i];
            sp_split[t][i] = sp_split[t - 1][i];
        } else {
            sp[t][i] = sp[t - 1][sp[t - 1][i]];
            sp_dist[t][i] = max(sp_dist[t - 1][i], sp_dist[t - 1][sp[t - 1][i]]);
            sp_split[t][i].ans = max({ sp_split[t - 1][sp[t - 1][i]].ans, sp_split[t - 1][i].ans, sp_split[t - 1][sp[t - 1][i]].posde + sp_split[t - 1][i].negde });
            sp_split[t][i].posde = max(sp_split[t - 1][sp[t - 1][i]].posde, sp_split[t - 1][i].posde);
            sp_split[t][i].negde = max(sp_split[t - 1][sp[t - 1][i]].negde, sp_split[t - 1][i].negde);
        }
    }
    int res = 2 * (n - 1) - dist[0];
    for (auto [ i, j, w ]: adj) {
        A = B = -1;
        int l = lca(i, j);
        int ds = depth[i] + depth[j] - depth[l] - depth[l];
        int curr = w + 2 * (n - 1) - ds - 1;
        if (A == -1) A = (i == l ? -1 : pr(i, depth[i] - depth[l] - 1));
        if (B == -1) B = (j == l ? -1 : pr(j, depth[j] - depth[l] - 1));
        int y = max(rev_dist[l] - 1, query_sp_dist(i, j, l, A, B) - 1);
        if (A != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[A] + 1));
        if (B != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[B] + 1));
        int G = 0;
        if (!lt_depth[l].empty()) G = *lt_depth[l].rbegin();
        else y = max(y, rev_max_depth[l] - 1);
        if ((int)lt_depth[l].size() > 1) y = max(y, *lt_depth[l].rbegin() + *prev(prev(lt_depth[l].end())) - 1);
        if (A != -1) lt_depth[l].insert(max_depth[A] + 1);
        if (B != -1) lt_depth[l].insert(max_depth[B] + 1);
        int Alt = (A == -1 ? (int)-1e9 : query_sp_half(A, i) + depth[l]);
        int Brt = (B == -1 ? (int)-1e9 : query_sp_half(B, j) + depth[l]);
        int Lt = max(rev_max_depth[l], G);
        y = max(y, Alt + max(Brt, Lt) + 1);
        y = max(y, max(Alt, Lt) + Brt + 1);
        if (A != -1) y = max(y, query_sp_res(A, i) + 1);
        if (B != -1) y = max(y, query_sp_res(B, j) + 1);
        res = min(res, curr - y);
    }
    printf("%d", res);
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:182:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  182 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp:185:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  185 |         scanf("%d%d%d", &x, &y, &w);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 2 / 2
• Subtask 3: 2 / 2
• Subtask 4: 6 / 6
• Subtask 5: 2 / 2
• Subtask 6: 3 / 3
• Subtask 7: 5 / 5
• Subtask 8: 0 / 4