提出 #57463036

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ソースコード 拡げる

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using pl = pair<ll, ll>;
constexpr ll INF = 1e9 + 7;
constexpr ll mod = 1e9 + 7;
constexpr ld eps = 1e-9;
const ld PI = acos(-1);

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n;
    cin >> n;
    vector<vector<int>> g(n);
    for (int i = 0; i < n - 1; ++i) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    vector<int> sz(n, 0);
    auto dfs = [&](auto &&dfs, int v, int p) -> void {
        sz[v] = 1;
        for (auto to: g[v]) {
            if (to == p)continue;
            dfs(dfs, to, v);
            sz[v] += sz[to];
        }
    };
    dfs(dfs, 0, -1);
    auto find = [&](auto &&find, int v, int p) -> int {
        int mx = n - sz[v];
        for (auto to: g[v]) {
            if (to == p)continue;
            int it = find(find, to, v);
            if (~it)return it;
            mx = max(mx, sz[to]);
        }
        return mx <= n / 2 ? v : -1;
    };
    int v = find(find, 0, -1);
    vector<pl> res;
    vector<vector<int>> all;
    auto go = [&](auto &&go, int v, int p, int id) -> void {
        if (~id)all[id].push_back(v);
        for (auto to: g[v]) {
            if (to == p)continue;
            int it = id;
            if (!~it) {
                it = all.size();
                all.emplace_back();
            }
            go(go, to, v, it);
        }
    };
    go(go, v, -1, -1);
    set<pl> s;
    for (int i = 0; i < all.size(); ++i) {
        s.insert(pl{(ll)all[i].size(),i});
    }
    while(s.size() > 1){
        auto x = *s.rbegin();
        s.erase(x);
        auto y = *s.rbegin();
        s.erase(y);
        x.first--;
        y.first--;
        res.push_back({all[x.second].back(),all[y.second].back()});
        all[x.second].pop_back();
        all[y.second].pop_back();
        if(x.first)s.insert(x);
        if(y.first)s.insert(y);
    }
    assert(s.size() <= 1);
    if (s.size()) {
        auto [val,who] = *s.begin();
        assert(val == 1);
        res.push_back({v, all[who].back()});
    }
    for (auto [x, y]: res) {
        cout << x + 1 << " " << y + 1 << "\n";
    }
}

提出情報

コンパイルエラー

Main.cpp: In function ‘int main()’:
Main.cpp:62:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<std::vector<int> >::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   62 |     for (int i = 0; i < all.size(); ++i) {
      |                     ~~^~~~~~~~~~~~

ジャッジ結果