Submission #1060398

#	Time	Username	Problem	Language	Result	Execution time	Memory
1060398		steveonalex	Sorting (IOI15_sorting)	C++17	100 / 100	617 ms	103872 KiB

sorting

#include <bits/stdc++.h>
#include "sorting.h"
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }

struct DSU{
    int n;
    vector<int> parent, sz;
    vector<pair<int, int>> history;

    DSU(int _n){
        n = _n;
        parent.resize(n); sz.resize(n, 1);
        for(int i = 0; i<n; ++i) parent[i] = i;
    }

    int find_set(int u){return (u == parent[u]) ? u : find_set(parent[u]);}
    bool same_set(int u, int v){return find_set(u) == find_set(v);}

    bool join_set(int u, int v){
        u = find_set(u), v = find_set(v);
        if (u != v){
            if (sz[u] < sz[v]) swap(u, v);
            parent[v] = u;
            sz[u] += sz[v];
            history.push_back({u, v});
            return true;
        }
        return false;
    }

    int get_size(int u){return sz[find_set(u)];}

    int get_version(){return history.size();}
    void roll_back(int version){
        while(get_version() > version){
            int u, v;
            tie(u, v) = history.back(); history.pop_back();
            parent[v] = v;
            sz[u] -= sz[v];
        }
    }
};

const int N = 2e5 + 69;
vector<pair<int, int>> st[N * 4];
int R;

void update(int u, int v, pair<int, int> val, int l, int r, int id){
    if (val.first == val.second) return;
    if (u <= l && r <= v){
        st[id].push_back(val);
        return;
    }
    int mid = (l + r) >> 1;
    if (u <= mid) update(u, v, val, l, mid, id * 2);
    if (v > mid) update(u, v, val, mid + 1, r, id * 2 + 1);
}

void traverse(int l, int r, int id, DSU &mst){
    int cur = mst.get_version();
    for(pair<int, int> i: st[id]) mst.join_set(i.first, i.second);
    if (l == r){
        if (mst.get_version() <= l) R = l;
        mst.roll_back(cur);
        return;
    }
    int mid = (l + r) >> 1;
    if (R == -1) traverse(l, mid, id * 2, mst);
    if (R == -1) traverse(mid + 1, r, id * 2 + 1, mst);
    mst.roll_back(cur);
}

int findSwapPairs(int n, int a[], int m, int x[], int y[], int p[], int q[]) {
    R = -1;
    minimize(m, n);
    vector<int> perm(n);
    for(int i = 0; i < n; ++i) perm[i] = a[i];

    for(int i = 0; i<=m*4+4; ++i) st[i].clear();
    vector<int> mp(n, 0);
    for(int i = 1; i<=m; ++i){
        int u = x[i-1], v = y[i-1];
        if (u == v) continue;
        update(mp[u], i-1, {u, perm[u]}, 0, m, 1);
        update(mp[v], i-1, {v, perm[v]}, 0, m, 1);
        mp[u] = mp[v] = -1;
        swap(perm[u], perm[v]);
        mp[u] = mp[v] = i;
    }

    for(int i = 0; i < n; ++i) if (mp[i] != -1){
        update(mp[i], m, {i, perm[i]}, 0, m, 1);
    }

    DSU mst(n);
    mst.history.reserve(n);
    traverse(0, m, 1, mst);

    for(int i = 0; i < n; ++i) perm[i] = a[i];
    for(int i = 0; i < R; ++i) swap(perm[x[i]], perm[y[i]]);

    vector<bool> visited(n);
    vector<pair<int,int>> swaps;
    for(int i = 0; i<n; ++i) if (!visited[i]) {
        int u = i;
        while(!visited[u]){
            visited[u] = true;
            if (!visited[perm[u]]) swaps.push_back({u, perm[u]});
            u = perm[u];
        }
    }

    reverse(ALL(swaps));
    vector<int> pos(n);
    for(int i = 0; i<n; ++i) perm[i] = a[i];
    for(int i = 0; i<n; ++i) pos[perm[i]] = i;
    for(int i = 0; i < R; ++i){
        int u = x[i], v = y[i];
        swap(perm[u], perm[v]);
        swap(pos[perm[u]], pos[perm[v]]);
        if (swaps.size()){
            u = pos[swaps.back().first], v = pos[swaps.back().second];
            swaps.pop_back();
        }
        else u = v = 0;
        swap(perm[u], perm[v]);
        swap(pos[perm[u]], pos[perm[v]]);

        p[i] = u, q[i] = v;
    }

    return R;
}

// int main(void){
//     ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

//     clock_t start = clock();

//     int n; cin >> n;
//     int a[n];
//     for(int i = 0; i<n; ++i) cin >> a[i];

//     int m; cin >> m;
//     int x[m], y[m];
//     for(int i = 0; i<m; ++i) cin >> x[i] >> y[i];

//     int p[m], q[m];
//     memset(p, -1, sizeof p); memset(q, -1, sizeof q);

//     int r = findSwapPairs(n, a, m, x, y, p, q);
//     cout << r << "\n";
//     for(int i = 0; i < r; ++i) {
//         swap(a[x[i]], a[y[i]]);
//         swap(a[p[i]], a[q[i]]);
//         cout << p[i] << " " << q[i] << "\n"; 
//     }

//     for(int i = 0; i < n; ++i) cout << a[i] << " "; cout << "\n";

//     cerr << "Time elapsed: " << clock() - start << " ms\n";

//     return 0;
// }

/*
5
4 3 2 1 0
6
0 1
1 2
2 3
3 4
0 1
1 2

*/

Compilation message (stderr)

sorting.cpp: In member function 'int DSU::get_version()':
sorting.cpp:79:42: warning: conversion from 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   79 |     int get_version(){return history.size();}
      |                              ~~~~~~~~~~~~^~

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