Submission #1090219

#	Time	Username	Problem	Language	Result	Execution time	Memory
1090219		yogesh_sane	Group Photo (JOI21_ho_t3)	C++17	12 / 100	325 ms	512 KiB

Main

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <queue>
using namespace std;

int n;
vector<int>a;
vector<int>p;
int const inf = 1e9;
int count_inversions(){
    vector<int>idx(n+1);
    bool valid = true;
    for(int i = 1; i < n; i++){
        if(p[i]  < p[i-1]-1)
            valid = false;
    }
    if(!valid)
        return inf;
    for(int i = 0; i < n; i++)
        idx[p[i]] = i;
    int inv = 0;
    for(int i = 0; i < n; i++){
        for(int j = i+1; j < n; j++){
            if(idx[a[i]] > idx[a[j]])
                inv++;
        }
    }
    return inv;
}
void subtask1(){
    p.resize(n);
    iota(p.begin(), p.end(), 1);
    int ans = inf;
    do{
        ans = min(ans, count_inversions());
    }while(next_permutation(p.begin(), p.end()));
    cout << ans << '\n';
}
void process_seq(){

}
void subtask2(){
    p.resize(n);
    iota(p.begin(), p.end(), 1);
    int ans = inf;
    for(int i = 0; i < (1<<(n)); i++){
        vector<int>ss;
        for(int j = 0; j < n; j++){
            if(i & (1<<j)){
                ss.push_back(j);
            }
        }
        if(ss.size() == 0 || (ss.size() > 1 && ss[0] == 0))
            continue;
        reverse(p.begin(), p.begin()+ss[0]);
        for(int j = 1; j < ss.size(); j++){
            reverse(p.begin()+ss[j-1], p.begin()+ss[j]);
        }
        reverse(p.begin()+ss.back(), p.end());
        ans = min(ans, count_inversions());
        reverse(p.begin(), p.begin()+ss[0]);
        for(int j = 1; j < ss.size(); j++){
            reverse(p.begin()+ss[j-1], p.begin()+ss[j]);
        }
        reverse(p.begin()+ss.back(), p.end());
    }
    cout << ans << '\n';
}
int main(){
    cin >> n;
    a.resize(n);
    for(int i = 0; i < n; i++)
        cin >> a[i];
    if(n <= 9){
        subtask1();
    }else if(n <= 20){
        subtask2();
    }
    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'void subtask2()':
Main.cpp:58:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |         for(int j = 1; j < ss.size(); j++){
      |                        ~~^~~~~~~~~~~
Main.cpp:64:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |         for(int j = 1; j < ss.size(); j++){
      |                        ~~^~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 0 / 32
• Subtask 4: 0 / 20
• Subtask 5: 0 / 36