Submission #440702

#	Time	Username	Problem	Language	Result	Execution time	Memory
440702		parsabahrami	Special graph (IZhO13_specialg)	C++17	100 / 100	80 ms	15372 KiB

specialg

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

typedef long long int ll;
typedef pair<int, int> pii;
 
#define SZ(x)                       (int) x.size()
#define F                           first
#define S                           second

const int N = 1e5 + 10, MOD = 1e9 + 7;
int H[N], St[N], R[N], M[N], M2[N], Ft[N], t[N], A[N], B[N], rt[N], nxt[N], n, q, tim;
vector<int> adj[N]; pii E[N];

int preFind(int v) {
    return !rt[v] ? v : rt[v] = preFind(rt[v]);
}

int Find(int v) {
    if (!rt[v]) return v;
    int p = rt[v]; rt[v] = Find(rt[v]), H[v] += H[p];
    return rt[v];
}

void preDFS(int v) {
    St[v] = tim++; M2[v] = 1;
    for (int &u : adj[v])  
        preDFS(u);
    Ft[v] = tim;
}

int D(int u, int v) {
    assert(Find(u) == Find(v));
    if (!(St[v] <= St[u] && Ft[u] <= Ft[v])) return MOD;
    return H[u] - H[v];
}

int query(int u, int v) {
    if (Find(u) != Find(v)) return -1;
    int ret = D(u, v);
    if (E[Find(u)].F) 
        ret = min(ret, D(u, E[Find(u)].F) + D(E[Find(u)].S, v) + 1);
    return ret >= MOD ? -1 : ret;
}

int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        scanf("%d", &nxt[i]);
    }
    scanf("%d", &q);
    for (int i = 1; i <= q; i++) {
        scanf("%d", &t[i]);
        if (t[i] > 1) scanf("%d%d", &A[i], &B[i]);
        else scanf("%d", &A[i]), M[A[i]] = 1;
    }
    for (int i = 1; i <= n; i++) {
        if (!M[i] && nxt[i]) {
            int u = preFind(i), v = preFind(nxt[i]);
            if (u != v) {
                adj[nxt[i]].push_back(u), assert(u == i), rt[u] = v;
            }
        }
    }
    for (int i = q; i; i--) {
        if (t[i] > 1) continue;
        int v = A[i], u = preFind(nxt[A[i]]); assert(nxt[A[i]]);
        if (u == v) continue;
        adj[nxt[v]].push_back(v), rt[v] = u;
    }
    for (int i = 1; i <= n; i++) 
        if (!M2[i] && preFind(i) == i) preDFS(i);
    memset(rt, 0, sizeof rt);
    for (int i = 1; i <= n; i++) {
        if (!M[i] && nxt[i]) {
            int u = Find(i), v = Find(nxt[i]); assert(u == i);
            if (u == v) E[i] = {i, nxt[i]};
            else {
                H[i] = H[nxt[i]] + 1;
                rt[i] = v;
            }
        }
    }
    for (int i = q; i; i--) {
        if (t[i] < 2) {
            int u = Find(A[i]), v = Find(nxt[A[i]]); assert(u == A[i]), assert(nxt[A[i]]);
            if (u == v) E[A[i]] = {A[i], nxt[A[i]]};
            else H[A[i]] = H[nxt[A[i]]] + 1, rt[A[i]] = v;
        } else {
            R[i] = query(A[i], B[i]);
        }
    }
    for (int i = 1; i <= q; i++) 
        if (t[i] > 1) printf("%d\n", R[i]);
    return 0;
}

Compilation message (stderr)

specialg.cpp: In function 'int main()':
specialg.cpp:48:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
specialg.cpp:50:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         scanf("%d", &nxt[i]);
      |         ~~~~~^~~~~~~~~~~~~~~
specialg.cpp:52:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |     scanf("%d", &q);
      |     ~~~~~^~~~~~~~~~
specialg.cpp:54:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |         scanf("%d", &t[i]);
      |         ~~~~~^~~~~~~~~~~~~
specialg.cpp:55:28: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   55 |         if (t[i] > 1) scanf("%d%d", &A[i], &B[i]);
      |                       ~~~~~^~~~~~~~~~~~~~~~~~~~~~
specialg.cpp:56:19: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |         else scanf("%d", &A[i]), M[A[i]] = 1;
      |              ~~~~~^~~~~~~~~~~~~

• Subtask 1: 100 / 100