Submission #774891

#	Time	Username	Problem	Language	Result	Execution time	Memory
774891		huutuan	Xor Sort (eJOI20_xorsort)	C++14	100 / 100	7 ms	1492 KiB

xorsort

#include <bits/stdc++.h>
 
using namespace std;
 
#define int long long
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((int)x.size())
#define sumof(x) accumulate(all(x), 0ll)
 
const int N=1001;
int n, s, a[N];
 
void solve(int tc){
    // cout << "Case #" << tc << ": ";
    vector<pair<int, int>> v;
    cin >> n >> s;
    for (int i=1; i<=n; ++i) cin >> a[i];
    if (n<=200){
        vector<int> vv(a+1, a+n+1);
        for (int i=1; i<n; ++i) v.emplace_back(i, i+1);
        int m=n;
        for (int i=1; i<m; ++i){
            int j=max_element(all(vv))-vv.begin()+1;
            for (int k=j; k<n; ++k) v.emplace_back(k+1, k);
            for (int k=max(1ll, j-1); k<n; ++k) v.emplace_back(k, k+1);
            vv.erase(vv.begin()+j-1);
            --n;
        }
        cout << sz(v) << '\n';
        for (auto& i:v) cout << i.first << ' ' << i.second << '\n';
        return;
    }
    for (int i=19; i>=0; --i){
        vector<int> idx;
        for (int j=1; j<=n; ++j) if (a[j]>>i&1) idx.push_back(j);
        if (idx.empty()) continue;
        for (int j=1; j<sz(idx); ++j){
            int i1=idx[j-1], i2=idx[j];
            for (int k=i1; k<i2-1; ++k){
                v.emplace_back(k+1, k);
                a[k+1]^=a[k];
                v.emplace_back(k, k+1);
                a[k]^=a[k+1];
            }
            v.emplace_back(i2-1, i2);
            a[i2-1]^=a[i2];
        }
        if (idx.back()!=n){
            for (int j=idx.back(); j<n; ++j){
                v.emplace_back(j+1, j);
                a[j+1]^=a[j];
                v.emplace_back(j, j+1);
                a[j]^=a[j+1];
            }
        }
        --n;
    }
    cout << sz(v) << '\n';
    for (auto& i:v) cout << i.first << ' ' << i.second << '\n';
}
 
int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int ntests=1;
    // cin >> ntests;
    for (int i=1; i<=ntests; ++i) solve(i);
    return 0;
}

• Subtask 1: 25 / 25
• Subtask 2: 35 / 35
• Subtask 3: 40 / 40