Submission #1065831

#	Time	Username	Problem	Language	Result	Execution time	Memory
1065831		anango	Sorting (IOI15_sorting)	C++17	74 / 100	1016 ms	22444 KiB

sorting

#include "sorting.h"
#include <bits/stdc++.h>
using namespace std;
int n;


vector<vector<int>> getcycledecomposition(vector<int> p) {
    vector<int> visited(n,0);
    vector<vector<int>> cycles;
    for (int i=0; i<n; i++) {
        if (!visited[i]) {
            visited[i] = 1;
            vector<int> cycle={i};
            while (p[cycle.back()]!=i) {
                visited[p[cycle.back()]] = 1;
                cycle.push_back(p[cycle.back()]);
            }
            cycles.push_back(cycle);
        }
    }
    return cycles;
}


int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    int l = 0;
    int r = M;
    while (l<r) {
        int m = (l+r)/2;
        n=N;
        vector<int> rev(n); for (int i=0; i<n; i++) rev[i] = i;
        vector<int> revpos(n); for (int i=0; i<n; i++) revpos[i] = i;
        vector<int> pos(n); for (int i=0; i<n; i++) pos[i] = i;
        vector<int> seq(n); for (int i=0; i<n; i++) seq[i] = S[i];
        for (int i=0; i<m; i++) {
            swap(pos[X[i]],pos[Y[i]]);
        }
        vector<int> reqperm(n,-1); for (int i=0; i<n; i++) reqperm[i] = seq[pos[i]];
        vector<int> reverse_finalpos(n,-1); for (int i=0; i<n; i++) reverse_finalpos[pos[i]] = i;
        vector<vector<int>> cycles = getcycledecomposition(reqperm);
        vector<pair<int,int>> swaps;
        for (auto i:cycles) {
            for (int j=1; j<i.size(); j++) {
                swaps.push_back({i[0],i[j]});
            }
        }
        reverse(swaps.begin(), swaps.end());
        vector<int> state(n); for (int i=0; i<n; i++) state[i] = i; 
        if (swaps.size()>m) {
            l=m+1;
            r=r;
        }
        else {
            l=l;
            r=m;
        }
        
    }
    M = l;
	 n=N;
    vector<int> rev(n); for (int i=0; i<n; i++) rev[i] = i;
    vector<int> revpos(n); for (int i=0; i<n; i++) revpos[i] = i;
    vector<int> pos(n); for (int i=0; i<n; i++) pos[i] = i;
    vector<int> seq(n); for (int i=0; i<n; i++) seq[i] = S[i];
    for (int i=0; i<M; i++) {
        swap(pos[X[i]],pos[Y[i]]);
    }
    vector<int> reqperm(n,-1); for (int i=0; i<n; i++) reqperm[i] = seq[pos[i]];
    vector<int> reverse_finalpos(n,-1); for (int i=0; i<n; i++) reverse_finalpos[pos[i]] = i;
    vector<vector<int>> cycles = getcycledecomposition(reqperm);
    vector<pair<int,int>> swaps;
    for (auto i:cycles) {
        for (int j=1; j<i.size(); j++) {
            swaps.push_back({i[0],i[j]});
        }
    }
    reverse(swaps.begin(), swaps.end());
    vector<int> state(n); for (int i=0; i<n; i++) state[i] = i; //the current 'pos'
    //swaps={{0,3},{0,2}};
    while (swaps.size()<M) {
        swaps.push_back({0,0});
    }
    
    vector<int> revperm(n); for (int i=0; i<n; i++) revperm[S[i]] = i;
    vector<int> perm(n); for (int i=0; i<n; i++) perm[i] = S[i];
    int bloaters = 0;
    for (int i=0; i<n; i++) {
        if (perm[i]!=i) bloaters++;
    }
    int lastswap = -1;
    for (int sw=0; sw<M; sw++) {
        swap(revperm[perm[X[sw]]],revperm[perm[Y[sw]]]);
        bloaters-=perm[X[sw]]!=X[sw];
        bloaters-=perm[Y[sw]]!=Y[sw];
        swap(perm[X[sw]],perm[Y[sw]]);
        bloaters+=perm[X[sw]]!=X[sw];
        bloaters+=perm[Y[sw]]!=Y[sw];
        pair<int,int> swp = swaps[sw];
        int a = swp.first;
        int b = swp.second;
        //cout << "trying2 " << a <<" " << b << endl;
        a=revperm[a]; b=revperm[b];
        //cout << "trying3 " << a <<" " << b << endl;
        swap(revperm[perm[a]],revperm[perm[b]]);
        bloaters-=perm[a]!=a;
        bloaters-=perm[b]!=b;
        swap(perm[a],perm[b]);
        bloaters+=perm[a]!=a;
        bloaters+=perm[b]!=b;
        P[sw] = a; Q[sw] = b;
        //cout << "swapping " << a <<" " << b<<endl;
        //cout << "ITERATION " << sw << endl;
        for (int i=0; i<n; i++) {
            assert(revperm[perm[i]]==i);
        }
        if (bloaters==0) {
            lastswap=sw;
            break;
        }
        /*for (int i=0; i<n; i++) {
            cout << revperm[i] <<" ";
        }
        cout << endl;
        for (int i=0; i<n; i++) {
            cout << perm[i] <<" ";
        }
        cout << endl;*/
    }
    
    
 
    /*for (int i=0; i<n; i++) {
        cout << pos[i] << " ";
    }
    cout << endl;
    for (int i=0; i<swaps.size(); i++) {
        cout << swaps[i].first <<" " << swaps[i].second << endl;
    }
    cout << endl;
    for (int i=0; i<n; i++) {
        cout << reqperm[i] << " ";
    }
    cout << endl;*/
    vector<int> cur(n); for (int i=0; i<n; i++) cur[i] = S[i];
    /*for (int i=0; i<M; i++) {
        swap(cur[X[i]],cur[Y[i]]);
        swap(cur[P[i]],cur[Q[i]]);
    }
    for (int i=0; i<n; i++) {
        assert(cur[i]==i);
        if (cur[i]!=i) {
            while (1) {
                int o=0;
            }
        }
    }*/
    /*cout << "final result" << endl;
    for (int i=0; i<n; i++) {
        cout << cur[i] <<" ";
    }
    cout << endl;*/
 
	return lastswap+1;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:43:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |             for (int j=1; j<i.size(); j++) {
      |                           ~^~~~~~~~~
sorting.cpp:49:25: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   49 |         if (swaps.size()>m) {
      |             ~~~~~~~~~~~~^~
sorting.cpp:73:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   73 |         for (int j=1; j<i.size(); j++) {
      |                       ~^~~~~~~~~
sorting.cpp:80:24: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   80 |     while (swaps.size()<M) {
      |            ~~~~~~~~~~~~^~

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 18 / 18
• Subtask 5: 20 / 20
• Subtask 6: 0 / 26