Submission #413522

#	Time	Username	Problem	Language	Result	Execution time	Memory
413522		JerryLiu06	Regions (IOI09_regions)	C++17	100 / 100	4766 ms	32560 KiB

regions

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using db = long double;
using str = string;

using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;

using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vpi = vector<pi>;
using vpl = vector<pl>;
using vpd = vector<pd>;

#define mp make_pair
#define f first
#define s second

#define sz(x) (int)(x).size()
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define sor(x) sort(all(x))
#define ft front()
#define bk back()
#define pb push_back
#define pf push_front

#define lb lower_bound
#define ub upper_bound

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) FOR(i, 0, a)
#define ROF(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define R0F(i, a) ROF(i, 0, a)
#define EACH(a, x) for (auto& a : x)

const int MOD = 1e9 + 7;
const int MXN = 2e5 + 10;
const int MXR = 25010;
const ll INF = 1e18;

const int BLOCK = 450;

int N, R, Q; vi adj[MXN]; int L[MXN]; // L[i] = Region of i

int timer = 1, in[MXN], out[MXN]; vi S[MXR]; // Sorted list of {in, out} for each region

vi large; int child[BLOCK][MXN], par[BLOCK][MXN]; int ind[MXR]; 

// Preorder Traversal ~ O(N)

void DFS(int X, int P) {
    in[X] = timer++; S[L[X]].pb(X);
    
    EACH(Y, adj[X]) if (Y != P) DFS(Y, X); out[X] = timer - 1;
}
bool isAnc(int A, int B) { return in[A] <= in[B] && out[B] <= out[A]; }

// Generate child[][] and par[][] DFS ~ O(N)

int genChild(int X, int P, int reg) {
    int sub = (L[X] == reg); EACH(Y, adj[X]) if (Y != P) sub += genChild(Y, X, reg);

    child[ind[reg]][L[X]] += sub; return sub;
}
void genPar(int X, int P, int reg, int cnt) {
    par[ind[reg]][L[X]] += cnt; cnt += (L[X] == reg);

    EACH(Y, adj[X]) if (Y != P) genPar(Y, X, reg, cnt);
} 

// Get the answer when queried (A, B) ~ O(N)

int genAns(int A, int B) {
    int ans = 0; int L = 0, R = 0; int last = 0; deque<int> anc;

    while (L < sz(S[A]) || R < sz(S[B])) {
        if (L < sz(S[A]) && (R >= sz(S[B]) || in[S[A][L]] < in[S[B][R]])) {
            while (sz(anc) && !isAnc(anc.bk, S[A][L])) anc.pop_back(); anc.pb(S[A][L++]);
        }
        else { while (sz(anc) && !isAnc(anc.bk, S[B][R])) anc.pop_back(); ans += sz(anc); R++; }
    }
    return ans;
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);

    cin >> N >> R >> Q >> L[1];

    FOR(i, 2, N + 1) { int A; cin >> A >> L[i]; adj[A].pb(i), adj[i].pb(A); }

    DFS(1, 0); int cur = 0; FOR(i, 1, R + 1) if (sz(S[i]) >= BLOCK) large.pb(i), ind[i] = cur++;

    EACH(i, large) { genChild(1, 0, i); genPar(1, 0, i, 0); }

    F0R(i, Q) {
        int A, B; cin >> A>> B; 
        
        if (sz(S[A]) >= BLOCK) cout << par[ind[A]][B] << endl;

        else if (sz(S[B]) >= BLOCK) cout << child[ind[B]][A] << endl;

        else cout << genAns(A, B) << endl;
    }
}

Compilation message (stderr)

regions.cpp: In function 'void DFS(int, int)':
regions.cpp:42:20: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
   42 | #define EACH(a, x) for (auto& a : x)
      |                    ^~~
regions.cpp:62:5: note: in expansion of macro 'EACH'
   62 |     EACH(Y, adj[X]) if (Y != P) DFS(Y, X); out[X] = timer - 1;
      |     ^~~~
regions.cpp:62:44: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
   62 |     EACH(Y, adj[X]) if (Y != P) DFS(Y, X); out[X] = timer - 1;
      |                                            ^~~
regions.cpp: In function 'int genAns(int, int)':
regions.cpp:86:13: warning: this 'while' clause does not guard... [-Wmisleading-indentation]
   86 |             while (sz(anc) && !isAnc(anc.bk, S[A][L])) anc.pop_back(); anc.pb(S[A][L++]);
      |             ^~~~~
regions.cpp:86:72: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'while'
   86 |             while (sz(anc) && !isAnc(anc.bk, S[A][L])) anc.pop_back(); anc.pb(S[A][L++]);
      |                                                                        ^~~
regions.cpp:82:40: warning: unused variable 'last' [-Wunused-variable]
   82 |     int ans = 0; int L = 0, R = 0; int last = 0; deque<int> anc;
      |                                        ^~~~

• Subtask 1: 15 / 15
• Subtask 2: 85 / 85