Submission #1000173

#	Time	Username	Problem	Language	Result	Execution time	Memory
1000173		whatthemomooofun1729	Sorting (IOI15_sorting)	C++17	100 / 100	139 ms	23772 KiB

sorting

#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <stack>
#include <map>
#include <queue>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cstring>
#include <cmath>
#include <functional>
#include <cassert>
#include <iomanip>
#include <numeric>
#include <bitset>
#include <sstream>
#include <chrono>
#include <random>

#define ff first
#define ss second
#define PB push_back
#define sz(x) int(x.size())
#define rsz resize
#define fch(xxx, yyy) for (auto xxx : yyy) // abusive notation
#define all(x) (x).begin(),(x).end()
#define eps 1e-9

// more abusive notation (use at your own risk):
//#define int ll

using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;

// debugging
void __print(int x) {std::cerr << x;}
void __print(ll x) {std::cerr << x;} /* remember to uncomment this when not using THE MACRO */
void __print(unsigned x) {std::cerr << x;}
void __print(ull x) {std::cerr << x;}
void __print(float x) {std::cerr << x;}
void __print(double x) {std::cerr << x;}
void __print(ld x) {std::cerr << x;}
void __print(char x) {std::cerr << '\'' << x << '\'';}
void __print(const char *x) {std::cerr << '\"' << x << '\"';}
void __print(const string& x) {std::cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V> void __print(const pair<T, V> &x) {std::cerr << '{'; __print(x.ff); std::cerr << ", "; __print(x.ss); std::cerr << '}';}
template<typename T> void __print(const T& x) {int f = 0; std::cerr << '{'; for (auto &i: x) std::cerr << (f++ ? ", " : ""), __print(i); std::cerr << "}";}
void _print() {std::cerr << "]\n";}
template <typename T, typename... V> void _print(T t, V... v) {__print(t); if (sizeof...(v)) std::cerr << ", "; _print(v...);}
void println() {std::cerr << ">--------------------<" << endl;}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

// templates
template <class T> bool ckmin(T &a, const T &b) {return b<a ? a = b, 1 : 0;}
template <class T> bool ckmax(T &a, const T &b) {return b>a ? a = b, 1 : 0;}
template <class T> using gr = greater<T>;
template <class T> using vc = vector<T>;
template <class T> using p_q = priority_queue<T>;
template <class T> using pqg = priority_queue<T, vc<T>, gr<T>>;
template <class T1, class T2> using pr = pair<T1, T2>;
mt19937_64 rng_ll(chrono::steady_clock::now().time_since_epoch().count());
int rng(int M) {return (int)(rng_ll()%M);} /*returns any random number in [0, M) */

// const variables
constexpr int INF = (int)2e9;
constexpr int MOD = 998244353;
constexpr ll LL_INF = (ll)3e18;
constexpr int mod = (int)1e9 + 7;
constexpr ll inverse = 500000004LL; // inverse of 2 modulo 1e9 + 7

void setIO(const string& str) {// fast input/output
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (str.empty()) return;
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
}

vc<pii> findOperations(vector<int> v) {
    int N = sz(v);
    vc<pii> ops;
    vi idx(N);
    for (int i = 0; i < N; ++i) {
        idx[v[i]] = i;
    }
//    debug(v);
//    debug(idx);
    for (int i = 0; i < N; ++i) {
        // place i here
//        debug(i);
//        debug(idx);
        if (idx[i] != i) {
            int a = i, b = idx[i];
//            debug(a, b);
            ops.PB({a, b});
            swap(idx[i], idx[v[i]]);
            swap(v[a], v[b]);
        }
    }
//    debug(v);
    reverse(all(ops));
    return ops;
}

int findSwapPairs(int N, int* s, int M, int* x, int* y, int* p, int* q) {
    vc<pii> ans; // answer (the set of operations needed)
    int l = 0, r = M; // bounds on binary search
    // note that the array can already be sorted, so l is within [0, M]
    while (l <= r) {
        int mid = (l + r) / 2; // assume that 'mid' moves are taken
        vi v(N);
        for (int i = 0; i < N; ++i) {
            v[i] = s[i]; // stores the apples in their original order on the plates from 0 to N - 1
        }
        for (int i = 0; i < mid; ++i) { // O(LogM)
            swap(v[x[i]], v[y[i]]); // now, swap the apples
        }
        vc<pii> ops = findOperations(v); // operations that make Aizhan win
        // ops -> swap the plates under the apples
        // if we end up with some permutation [v[0], ... v[N]]
        // we want the plates to be in that same orientation
        // or, we change [v[0], ... v[N]] -> [0, 1, 2, ... N] (1)
        // if we do (1), we need to reverse the list of operations before outputting
        if (sz(ops) <= mid) {
            r = mid - 1;
        } else {
            l = mid + 1;
        }
    }
    r++;
    // redo the above operations
    vi v(N);
    for (int i = 0; i < N; ++i) {
        v[i] = s[i];
    }
    for (int i = 0; i < r; ++i) {
        swap(v[x[i]], v[y[i]]);
    }
    ans = findOperations(v);
    // fill the rest of the operations if needed
    while (sz(ans) < r) {
        ans.PB({0, 0});
    }
    vi idx(N); // finding the index of an element a[i] in the array
    for (int i = 0; i < N; ++i) {
        idx[s[i]] = i;
        v[i] = s[i]; // resetting v
    }
    for (int i = 0; i < r; ++i) {
        swap(v[x[i]], v[y[i]]); // performing swap operations for Ermek
    }
    for (int i = 0; i < r; ++i) { // performing the swap operations for Aizhan
        swap(idx[s[x[i]]], idx[s[y[i]]]);
        swap(s[x[i]], s[y[i]]);
        // v[ans[i].ff] and v[ans[i].ss] are the apples corresponding to the plates that need to be flipped
        // idx[v[ans[i].ff]] and idx[v[ans[i].ss]] are the plates corresponding to the apples in the current array
        p[i] = idx[v[ans[i].ff]], q[i] = idx[v[ans[i].ss]]; // convert each swap to the index it is currently in and add it to (p, q)
        swap(idx[s[p[i]]], idx[s[q[i]]]); // flip/update
        swap(s[p[i]], s[q[i]]);
    }
    return r;
}

void solve() { // testing cases for this algorithm
    int N, M;
    int s[100005], x[100005], y[100005], p[100005], q[100005];
    cin >> N >> M;
    for (int i = 0; i < N; ++i) {
        cin >> s[i];
    }
    for (int i = 0; i < M; ++i) {
        cin >> x[i] >> y[i];
    }
    vi v(N);
    for (int i = 0; i < N; ++i) {
        v[i] = s[i];
    }
    int moves = findSwapPairs(N, s, M, x, y, p, q);
    cout << moves << '\n';
    for (int i = 0; i < moves; ++i) {
        cout << p[i] << ' ' << q[i] << '\n';
    }
    for (int i = 0; i < moves; ++i) {
        swap(v[x[i]], v[y[i]]);
        swap(v[p[i]], v[q[i]]);
    }
    cout << "resulting array: \n";
    for (int i = 0; i < N; ++i) {
        cout << v[i] << ' ';
    }
    cout << '\n';
}
/*
signed main() { // TIME YOURSELF !!!
    setIO("");
    solve();
}*/

// TLE -> TRY NOT USING DEFINE INT LONG LONG
// CE -> CHECK LINE 45
// 5000 * 5000 size matrices are kinda big (potential mle)
// Do something, start simpler

Compilation message (stderr)

sorting.cpp: In function 'void setIO(const string&)':
sorting.cpp:88:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |     freopen((str + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sorting.cpp:89:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |     freopen((str + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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