Submission #1284082

#	Time	Username	Problem	Language	Result	Execution time	Memory
1284082		nqc	Construction of Highway (JOI18_construction)	C++20	100 / 100	202 ms	21436 KiB

construction

#include<bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define ll long long
#define ull unsigned long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pli pair<ll, int>
#define debug(x) cout << #x << " = " << x << '\n'
#define all(a) a.begin(), a.end()
#define SZ(a) (int)(a).size()

const int N = 1e5 + 5;
const int mod = 1e9 + 7;
const ll inf64 = 3e18;
const int inf32 = 2e9 + 5;

struct FenwickTree {
    int n;
    vector<int> node, his;

    FenwickTree() {}

    void init(int _n) {
        n = _n;
        node.assign(n + 3, 0);
    }

    void upd(int i, int x) {
        for(; i <= n; i += i & (-i)) {
            node[i] += x;
            his.push_back(i);
        }
    }

    int get(int i) {
        int res = 0;
        for(; i; i -= i & (-i)) 
            res += node[i];
        return res;
    }

    void reset() {
        for(int i : his) 
            node[i] = 0;
        his.clear();
    }
};
FenwickTree fen;

int n, a[N];
vector<int> g[N];
vector<pii> edges;

void compress() {
    pii b[n + 3];
    for(int i = 1; i <= n; i++) 
        b[i] = make_pair(a[i], i);
    sort(b + 1, b + 1 + n);
    for(int i = 1, id = 0; i <= n; i++) {
        id += i == 1 || b[i].fi != b[i - 1].fi;
        a[b[i].se] = id;
    }
}

int h[N], par[N], hev[N], head[N];
vector<pii> dat[N];
bool exist[N];

int dfs_tree(int u) {
    int sz = 1, mx = 0;
    for(int v : g[u]) {
        par[v] = u, h[v] = h[u] + 1;

        int szc = dfs_tree(v);
        sz += szc;
        if(szc > mx) mx = szc, hev[u] = v;
    }
    return sz;
}

void decompose(int u, int top) {
    head[u] = top;
    if(hev[u]) decompose(hev[u], top);

    for(int v : g[u]) 
        if(v != hev[u]) decompose(v, v);
}

void update(int u, int x) {
    while(u) {
        int v = head[u], c;
        while(SZ(dat[v]) && h[dat[v].back().se] <= h[u]) {
            c = dat[v].back().fi;
            dat[v].pop_back();
        }

        if(SZ(dat[v])) {
            if(dat[v].back().se != hev[u]) dat[v].push_back({c, hev[u]});
        }
        else {
            if(exist[hev[u]]) dat[v].push_back({c, hev[u]});
        }
        dat[v].push_back({x, v});
        u = par[v];
    }
}

ll query(int u) {
    int U = u;
    vector<pii> vec;
    while(u) {
        int v = head[u];
        vector<pii> tmp;
        for(int i = SZ(dat[v]) - 1; i >= 0; i--) {
            if(h[dat[v][i].se] > h[u]) break;
            tmp.push_back(dat[v][i]);
        }
        for(int i = SZ(tmp) - 1; i >= 0; i--) 
            vec.push_back(tmp[i]);

        u = par[v];
    }

    ll ans = 0;
    for(int i = 0; i < SZ(vec); i++) {
        pii p = vec[i];
        int cnt = h[U] - h[p.se] + (i == 0);
        ans += 1ll * cnt * fen.get(p.fi - 1);
        fen.upd(p.fi, cnt);
        U = p.se;
    }
    fen.reset();
    return ans;
}

void solve() {
    cin >> n;
    for(int i = 1; i <= n; i++) 
        cin >> a[i];
    compress();
    for(int i = 1, u, v; i < n; i++) {
        cin >> u >> v;
        g[u].push_back(v);
        edges.push_back({u, v});
    }

    dfs_tree(1);

    decompose(1, 1);

    fen.init(n);
    dat[1].push_back({a[1], 1});
    exist[1] = true;
    for(pii e : edges) {
        int u, v;
        tie(u, v) = e;

        exist[v] = true;

        cout << query(u) << '\n';
        update(v, a[v]);
    }
}

int main() {
    auto start = chrono::steady_clock::now();

    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if(fopen("input.txt", "r")) {
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    }
    int test = 1; 
    // cin >> test;
    while(test--) solve();
    
    chrono::duration<double> elapsed {chrono::steady_clock::now() - start};
    cerr << "\n>> Runtime: " << elapsed.count() << "s\n";
}

Compilation message (stderr)

construction.cpp: In function 'int main()':
construction.cpp:173:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  173 |         freopen("input.txt", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
construction.cpp:174:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  174 |         freopen("output.txt", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 9 / 9
• Subtask 3: 84 / 84