Submission #594595

#	Time	Username	Problem	Language	Result	Execution time	Memory
594595		davi_bart	Sorting (IOI15_sorting)	C++14	56 / 100	1081 ms	8224 KiB

sorting

#pragma GCC optimize("O3")
#include <bits/stdc++.h>

#include "sorting.h"
using namespace std;
#define ll long long
// #define int ll
#define fi first
#define se second
#define ld long double
#define pb push_back
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int N;
struct Dsu {
    vector<int> par, dim;
    Dsu(vector<int> &k) {
        par.resize(N);
        dim = vector<int>(N, 1);
        iota(par.begin(), par.end(), 0);
        for (int i = 0; i < k.size(); i++) {
            unite(i, k[i]);
        }
    }
    int find(int pos) {
        return par[pos] = par[pos] == pos ? pos : find(par[pos]);
    }
    void unite(int a, int b) {
        a = find(a);
        b = find(b);
        if (a == b) return;
        if (dim[a] < dim[b]) swap(a, b);
        par[b] = a;
        dim[a] += dim[b];
    }
    int conta() {
        int tot = 0;
        for (int i = 0; i < N; i++) {
            if (i == par[i]) tot += dim[i] - 1;
        }
        return tot;
    }
};
vector<int> v;
vector<int> ini;
vector<pair<int, int>> scambi;
vector<bool> vis(200010);
void dfs(int pos, int ini) {
    vis[pos] = 1;
    scambi.pb({pos, v[pos]});
    if (v[pos] == ini) return;
    dfs(v[pos], ini);
}
int findSwapPairs(int N, int S[], int M, int P[], int Q[], int X[], int Y[]) {
    ::N = N;
    for (int i = 0; i < N; i++) v.pb(S[i]);
    ini = v;
    int ans = 0;
    for (int i = 0; i < M; i++) {
        Dsu dsu(v);
        // cout << dsu.conta() << " ";
        if (dsu.conta() <= i) {
            ans = i;
            break;
        }
        swap(v[P[i]], v[Q[i]]);
    }
    // cout << endl;
    // int o = 0;
    for (int i = 0; i < N; i++) {
        if (vis[i] || v[i] == i) continue;
        dfs(v[i], i);
    }
    // while (1) {
    //     int k = scambi.size();
    //     for (int i = 0; i < N; i++) {
    //         if (v[i] != i) {
    //             scambi.pb({v[i], i});
    //             swap(v[find(v.begin(), v.end(), i) - v.begin()], v[i]);
    //         }
    //     }
    //     if (k == scambi.size()) break;
    // }
    // ans = scambi.size();
    // for (auto [a, b] : scambi) cout << a << " " << b << endl;
    // assert(scambi.size() <= ans);
    v = ini;
    for (int i = 0; i < ans; i++) {
        swap(v[P[i]], v[Q[i]]);
        for (int j = 0; j < N; j++) {
            if (v[j] == scambi[i].fi) X[i] = j;
        }
        for (int j = 0; j < N; j++) {
            if (v[j] == scambi[i].se) Y[i] = j;
        }
        swap(v[X[i]], v[Y[i]]);
    }
    // v = ini;
    // for (int i = 0; i < ans; i++) {
    //     swap(v[P[i]], v[Q[i]]);
    //     swap(v[X[i]], v[Y[i]]);
    // }
    // for (int i = 0; i < N; i++) assert(v[i] == i);
    return ans;
}

Compilation message (stderr)

sorting.cpp: In constructor 'Dsu::Dsu(std::vector<int>&)':
sorting.cpp:20:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         for (int i = 0; i < k.size(); i++) {
      |                         ~~^~~~~~~~~~
sorting.cpp: In function 'void dfs(int, int)':
sorting.cpp:47:23: warning: declaration of 'ini' shadows a global declaration [-Wshadow]
   47 | void dfs(int pos, int ini) {
      |                   ~~~~^~~
sorting.cpp:44:13: note: shadowed declaration is here
   44 | vector<int> ini;
      |             ^~~
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:53:23: warning: declaration of 'N' shadows a global declaration [-Wshadow]
   53 | int findSwapPairs(int N, int S[], int M, int P[], int Q[], int X[], int Y[]) {
      |                   ~~~~^
sorting.cpp:13:5: note: shadowed declaration is here
   13 | int N;
      |     ^

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 0 / 18
• Subtask 5: 20 / 20
• Subtask 6: 0 / 26