Submission #251980

#	Time	Username	Problem	Language	Result	Execution time	Memory
251980		paradox	Sorting (IOI15_sorting)	C++17	100 / 100	375 ms	30496 KiB

sorting

#include "sorting.h"

#include <iostream>
#include <fstream>
#include <vector>
#include <set>
#include <map>
#include <cstring>
#include <string>
#include <cmath>
#include <cassert>
#include <ctime>
#include <algorithm>
#include <sstream>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <cstdlib>
#include <cstdio>
#include <iterator>
#include <functional>
#include <unordered_set>
#include <unordered_map>
using namespace std;
 
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define pii pair<int, int>
#define vi vector<int>
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)


typedef long long ll;
typedef short inth;
 
const int K = 6e5 + 7;
const int MOD = 1e9 + 7;
const ll INF = 1e16 + 17;

int m, n;
pii query[K], ans[K];

pii temp[K];

int pos[K];

bool check(int t, int S[]) {
    int out[n], in[n];
    for (int i = 0; i < n; ++i)
        out[i] = in[i] = S[i];

    for (int id = 0; id < t; ++id) {
        int i = query[id].fi, j = query[id].se;
        swap(out[i], out[j]);
    }

    bool us[n];
    memset(us, false, sizeof us);

    int cnt = 0;

    for (int i = 0; i < n; ++i) {
        if (us[i])
            continue;
        
        vi ord;
        int v = out[i];
        while (v != i) {
            ord.pb(v);
            us[v] = true;
            v = out[v];
        }
        ord.pb(v);
        us[v] = true;

        for (int j = sz(ord) - 1; j > 0; --j)
            temp[cnt++] = mp(ord[0], ord[j]);
    }

    if (cnt > t)
        return false;
    
    for (int i = 0; i < n; ++i)
        pos[in[i]] = i;

    for (int id = 0; id < cnt; ++id) {

        int i = query[id].fi, j = query[id].se;
        swap(in[i], in[j]);
        pos[in[i]] = i;
        pos[in[j]] = j;

        i = pos[temp[id].fi]; j = pos[temp[id].se];
        ans[id] = mp(i, j);
        swap(in[i], in[j]);
        pos[in[i]] = i;
        pos[in[j]] = j;
    }

    while (cnt < t)
        ans[cnt++] = mp(0, 0);

    return true;
}

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    int l = -1, r = M;

    m = M; n = N;
    for (int i = 0; i < m; ++i)
        query[i] = mp(X[i], Y[i]);

    while (r - l > 1) {
        int m = (l + r) >> 1;
        if (check(m, S)) {
            r = m;
        } else {
            l = m;
        }
    }
    check(r, S);
    for (int i = 0; i < r; ++i) {
        P[i] = ans[i].fi;
        Q[i] = ans[i].se;
    }
    return r;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:119:13: warning: declaration of 'm' shadows a global declaration [-Wshadow]
         int m = (l + r) >> 1;
             ^
sorting.cpp:45:5: note: shadowed declaration is here
 int m, n;
     ^

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