Submission #583811

#	Time	Username	Problem	Language	Result	Execution time	Memory
583811		InternetPerson10	Sorting (IOI15_sorting)	C++17	100 / 100	601 ms	26224 KiB

sorting

#include "sorting.h"
#include <bits/stdc++.h>
 
using namespace std;
 
bool trySwapPairs(int n, int S[], int m, int X[], int Y[], int P[], int Q[]) {
    vector<int> targetArr(n);
    vector<int> revInd(n);
    int countMatches = 0;
    for(int i = 0; i < n; i++) {
        targetArr[i] = i;
        if(S[i] == i) countMatches++;
    }
    for(int i = m-1; i >= 0; i--) {
        swap(targetArr[X[i]], targetArr[Y[i]]);
    }
    for(int i = 0; i < n; i++) {
        revInd[targetArr[i]] = i;
    }
    vector<int> notGood(n);
    for(int i = 0; i < n; i++) {
        if(S[i] != targetArr[i]) {
            notGood[i] = true;
        }
    }
    vector<int> nums(n);
    vector<int> otherRevInd(n);
    auto swapTwo = [&](int i, int a, int b) {
        if(a == S[a]) countMatches--;
        if(b == S[b]) countMatches--;
        swap(nums[otherRevInd[a]], nums[otherRevInd[b]]);
        swap(otherRevInd[a], otherRevInd[b]);
        swap(S[a], S[b]);
        P[i] = a; Q[i] = b;
        if(a == S[a]) countMatches++;
        if(b == S[b]) countMatches++;
    };
    vector<int> taken(n, false);
    vector<pair<int, int>> pairs;
    pairs.clear();
    for(int i = 0; i < n; i++) {
        taken[i] = false;
    }
    vector<int> v;
    for(int i = 0; i < n; i++) {
        otherRevInd[i] = i;
        nums[i] = i;
        if(taken[i]) continue;
        taken[i] = true;
        v.push_back(i);
        int x = revInd[S[i]];
        while(x != i) {
            taken[x] = true;
            v.push_back(x);
            x = revInd[S[x]];
        }
        for(int j = 1; j < v.size(); j++) {
            pairs.push_back({v[j-1], v[j]});
        }
        v.clear();
    }
    while(pairs.size() < m) pairs.push_back({0, 0});
    for(int i = 0; i < m; i++) {
        if(countMatches == n) {
            m = i;
            break;
        }
        if(X[i] != Y[i]) {
            if(X[i] == S[X[i]]) countMatches--;
            if(Y[i] == S[Y[i]]) countMatches--;
            swap(nums[otherRevInd[X[i]]], nums[otherRevInd[Y[i]]]);
            swap(otherRevInd[X[i]], otherRevInd[Y[i]]);
            swap(S[X[i]], S[Y[i]]);
            if(X[i] == S[X[i]]) countMatches++;
            if(Y[i] == S[Y[i]]) countMatches++;
        }
        swapTwo(i, nums[pairs[i].first], nums[pairs[i].second]);
        /*
        cout << "Current state: ";
        for(int j = 0; j < n; j++) cout << S[j] << ' ';
        cout << '\n';
        */
    }
    return (countMatches == n);
}
 
int findSwapPairs(int n, int R[], int m, int X[], int Y[], int P[], int Q[]) {
    int V[200001];
    int l = -1, r = min(m, n+1);
    while(l != r - 1) {
        for(int i = 0; i < n; i++) {
            V[i] = R[i];
        }
        int mid = (l + r + 1) / 2;
        if(trySwapPairs(n, V, mid, X, Y, P, Q)) r = mid;
        else l = mid;
    }
    trySwapPairs(n, R, r, X, Y, P, Q);
    return r;
}

Compilation message (stderr)

sorting.cpp: In function 'bool trySwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:57:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |         for(int j = 1; j < v.size(); j++) {
      |                        ~~^~~~~~~~~~
sorting.cpp:62:24: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   62 |     while(pairs.size() < m) pairs.push_back({0, 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