Submission #778393

#	Time	Username	Problem	Language	Result	Execution time	Memory
778393		danikoynov	Sorting (IOI15_sorting)	C++14	100 / 100	153 ms	18340 KiB

sorting

#include "sorting.h"
#include<bits/stdc++.h>

using namespace std;

const int maxn = 2e5 + 10;
int n, arr[maxn], used[maxn];
vector < pair < int, int > > edges;
int count_steps()
{
    for (int i = 0; i < n; i ++)
        used[i] = 0;
    int ans = 0;
    for (int i = 0; i < n; i ++)
    {
        if (used[i])
            continue;
        int v = arr[i], cnt = 0;
        while(v != i)
        {
            used[v] = 1;
            cnt ++;
            v = arr[v];
        }
        used[v] = 1;
        cnt ++;
        ans = ans + (cnt - 1);
    }
    return ans;
}

void build_edges()
{
    for (int i = 0; i < n; i ++)
        used[i] = 0;
    for (int i = 0; i < n; i ++)
    {
        if (used[i])
            continue;
        vector < int > ord;
        int v = arr[i];
        while(v != i)
        {
            ord.push_back(v);
            used[v] = 1;
            v = arr[v];
        }
        ord.push_back(i);
        used[i] = 1;

        for (int i = 0; i < ord.size() - 1; i ++)
            edges.push_back({arr[ord[i]], arr[ord[i + 1]]});
    }
}

int pos[maxn];
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[])
{
    n = N;
    bool sorted = true;
    for (int i = 0; i < N; i ++)
        if (S[i] != i)
            sorted = false;

    if (sorted)
        return 0;
    for (int i = 0; i < N; i ++)
        arr[i] = S[i];

    int l = 0, r = M - 1;
    while(l <= r)
    {
        int m = (l + r) / 2;
        for (int i = 0; i < N; i ++)
            arr[i] = S[i];
        for (int i = 0; i <= m; i ++)
            swap(arr[X[i]], arr[Y[i]]);
            //cout << "check " << m << " " << count_steps() << endl;
        if (count_steps() <= m + 1)
            r = m - 1;
        else
            l = m + 1;
    }
    int pivot = l;
        for (int i = 0; i < N; i ++)
            arr[i] = S[i];
        for (int i = 0; i <= pivot; i ++)
            swap(arr[X[i]], arr[Y[i]]);
    /**for (int i = 0; i < M; i ++)
    {
        swap(arr[X[i]], arr[Y[i]]);
        int steps = count_steps();

        if (steps <= i + 1)
        {
            pivot = i;
            break;
        }
    }
    cout << pivot << endl;*/
    ///assert(pivot != -1);
    ///cout << pivot << endl;
    ///exit(0);
    build_edges();
    for (int i = 0; i < n; i ++)
        pos[S[i]] = i, arr[i] = S[i];
    for (int i = 0; i < edges.size(); i ++)
    {
        swap(arr[X[i]], arr[Y[i]]);
    swap(pos[arr[X[i]]], pos[arr[Y[i]]]);

        ///cout << edges[i].first << " : " << edges[i].second << endl;
        P[i] = pos[edges[i].first];
        Q[i] = pos[edges[i].second];
        swap(arr[Q[i]], arr[P[i]]);
        swap(pos[edges[i].first], pos[edges[i].second]);

            ///cout << id1 << " : " << id2 << endl;

        ///swap(pos[X[i]], pos[Y[i]]);
    }
    int left = pivot - edges.size() + 1;
    if (left % 2 == 0)
    {
        for (int i = edges.size(); i <= pivot; i ++)
        {
            P[i] = 0;
            Q[i] = 1;
        }
    }
    else
    {
        for (int i = edges.size(); i < pivot; i ++)
        {
            P[i] = 0;
            Q[i] = 1;
        }
        P[pivot] = Q[pivot] = 0;
    }

    /**for (int i = 0; i <= pivot; i ++)
    { swap(S[X[i]], S[Y[i]]);
        swap(S[P[i]], S[Q[i]]);

    }*/
    /**for (int i = 0; i < N; i ++)
        cout << S[i] << " ";
    cout << endl;*/
    ///cout << "stop " << edges.size() << " " << pivot << endl;


    return pivot + 1;
}

Compilation message (stderr)

sorting.cpp: In function 'void build_edges()':
sorting.cpp:51:18: warning: declaration of 'i' shadows a previous local [-Wshadow]
   51 |         for (int i = 0; i < ord.size() - 1; i ++)
      |                  ^
sorting.cpp:36:14: note: shadowed declaration is here
   36 |     for (int i = 0; i < n; i ++)
      |              ^
sorting.cpp:51:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   51 |         for (int i = 0; i < ord.size() - 1; i ++)
      |                         ~~^~~~~~~~~~~~~~~~
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:107:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  107 |     for (int i = 0; i < edges.size(); i ++)
      |                     ~~^~~~~~~~~~~~~~
sorting.cpp:122:37: warning: conversion from 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
  122 |     int left = pivot - edges.size() + 1;
      |                ~~~~~~~~~~~~~~~~~~~~~^~~
sorting.cpp:125:32: warning: conversion from 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
  125 |         for (int i = edges.size(); i <= pivot; i ++)
      |                      ~~~~~~~~~~^~
sorting.cpp:133:32: warning: conversion from 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
  133 |         for (int i = edges.size(); i < pivot; i ++)
      |                      ~~~~~~~~~~^~

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