Submission #778271

#	Time	Username	Problem	Language	Result	Execution time	Memory
778271		boris_mihov	Sorting (IOI15_sorting)	C++17	100 / 100	158 ms	23628 KiB

sorting

#include "sorting.h"
#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>
#include <stack>
 
typedef long long llong;
const int MAXN = 200000 + 10;
const int INF  = 1e9;
 
int n;
int p[MAXN];
int pos[MAXN];
bool vis[MAXN];
std::vector <std::pair <int,int>> ops;
std::stack <std::pair <int,int>> st;
 
void getOps()
{
    ops.clear();
    std::fill(vis + 1, vis + 1 + n, false);
    for (int i = 1 ; i <= n ; ++i)
    {
        if (vis[i])
        {
            continue;
        }
 
        while (!st.empty())
        {
            st.pop();
        }
 
        int curr = i;
        while (!vis[curr])
        {
            vis[curr] = true;
            curr = p[curr];
        
            if (!vis[curr])
            {
                st.push({p[curr], p[i]});
            }
        }
 
        while (!st.empty())
        {
            ops.push_back(st.top());
            st.pop();
        }
    }
}
 
void makeSwap(int x, int y)
{
    std::swap(p[x], p[y]);
    pos[p[x]] = x;
    pos[p[y]] = y;
}
 
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) 
{
    n = N;
    for (int i = 1 ; i <= n ; ++i)
    {
        p[i] = S[i - 1] + 1;
    }
 
    getOps();
    if (ops.empty())
    {
        return 0;
    }
    
    int l = 0, r = M + 1, mid;
    while (l < r - 1)
    {
        mid = (l + r) / 2;
        for (int i = 1 ; i <= n ; ++i)
        {
            p[i] = S[i - 1] + 1;
        }

        for (int i = 1 ; i <= mid ; ++i)
        {
            std::swap(p[X[i - 1] + 1], p[Y[i - 1] + 1]);
        }

        getOps();
        if (ops.size() <= mid) r = mid;
        else l = mid;
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        p[i] = S[i - 1] + 1;
    }

    for (int i = 1 ; i <= r ; ++i)
    {
        std::swap(p[X[i - 1] + 1], p[Y[i - 1] + 1]);
    }
    
    getOps();
    while (ops.size() < r)
    {
        ops.push_back({1, 1});
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        p[i] = S[i - 1] + 1;
        pos[p[i]] = i;
    }
 
    for (int i = 0 ; i < ops.size() ; ++i)
    {
        makeSwap(X[i] + 1, Y[i] + 1);
        P[i] = pos[ops[i].first] - 1;
        Q[i] = pos[ops[i].second] - 1;
        makeSwap(P[i] + 1, Q[i] + 1);
    }
 
    for (int i = 1 ; i <= n ; ++i)
    {
        assert(p[i] == i);
    }
 
    return ops.size();
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:92:24: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   92 |         if (ops.size() <= mid) r = mid;
      |             ~~~~~~~~~~~^~~~~~
sorting.cpp:107:23: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  107 |     while (ops.size() < r)
      |            ~~~~~~~~~~~^~~
sorting.cpp:118:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  118 |     for (int i = 0 ; i < ops.size() ; ++i)
      |                      ~~^~~~~~~~~~~~
sorting.cpp:131:20: warning: conversion from 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
  131 |     return ops.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