Submission #108756

#	Time	Username	Problem	Language	Result	Execution time	Memory
108756		PeppaPig	Sorting (IOI15_sorting)	C++14	100 / 100	338 ms	21676 KiB

sorting

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

#define pii pair<int, int>
#define x first
#define y second

using namespace std;

const int N = 2e5+5;

int findSwapPairs(int n, int s[], int m, int x[], int y[], int p[], int q[]) {
    auto solve = [&](int k) {
        vector<int> v(s, s + n), pos(n);
        vector<pii> ret;
        for(int i = 0; i < k; i++) swap(v[x[i]], v[y[i]]);
        for(int i = 0; i < n; i++) pos[v[i]] = i;
        for(int i = 0; i < n; i++) if(v[i] != i) {
            ret.emplace_back(v[i], i);
            int now = v[i];
            swap(v[i], v[pos[i]]);
            swap(pos[now], pos[i]);
        }
        return ret;
    };

    int l = 0, r = m;
    while(l < r) {
        int mid = (l + r) >> 1;
        if(solve(mid).size() <= mid) r = mid;
        else l = mid+1;
    }

    vector<pii> ans = solve(r);
    vector<int> pos(n);
    for(int i = 0; i < n; i++) pos[s[i]] = i;
    for(int i = 0; i < r; i++) {
        swap(pos[s[x[i]]], pos[s[y[i]]]);
        swap(s[x[i]], s[y[i]]);

        if(i < ans.size()) {
            int a, b; tie(a, b) = ans[i];
            p[i] = pos[a], q[i] = pos[b];
            swap(s[pos[a]], s[pos[b]]);
            swap(pos[a], pos[b]);
        }
    }
    for(int i = ans.size(); i < r; i++) p[i] = 0, q[i] = 0;

    return r;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:30:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(solve(mid).size() <= mid) r = mid;
            ~~~~~~~~~~~~~~~~~~^~~~~~
sorting.cpp:41:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(i < ans.size()) {
            ~~^~~~~~~~~~~~
sorting.cpp:48:25: warning: conversion to 'int' from 'std::vector<std::pair<int, int> >::size_type {aka long unsigned int}' may alter its value [-Wconversion]
     for(int i = ans.size(); i < r; i++) p[i] = 0, q[i] = 0;
                 ~~~~~~~~^~

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