Submission #1307492

#TimeUsernameProblemLanguageResultExecution timeMemory
1307492hectormedranoArranging Shoes (IOI19_shoes)C++20
10 / 100
4 ms6468 KiB
#include <cstdio>
#include <cassert>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

vector<ll> st(8e5+5, 0);

void update(ll l, ll r, ll ind, ll pos){
    if(l == r){st[ind]++; return;}
    ll m = (l+r)/2;
    if(pos<=m){
        update(l, m, 2*ind, pos);
    } else {
        update(m+1, r, 2*ind+1, pos);
    }
    st[ind] = st[2*ind] + st[2*ind+1];
}

ll query(ll l, ll r, ll ind, ll ql, ll qr){
    if(r<ql or qr<l){return 0;}
    if(ql<=l and r<=qr){return st[ind];}
    ll m = (l+r)/2;
    return query(l, m, 2*ind, ql, qr) + query(m+1, r, 2*ind+1, ql, qr);
}

ll count_swaps(vector<int> s) {
    ll inv = 0;
    ll n = s.size();
    n = n/2;
    vector<pair<ll, ll>> a;
    vector<bool> u(2*n, false);
    for(ll i=0;i<2*n;i++){
        if(s[i]<0){
            a.push_back({s[i], i});
            u[i] = true;
            for(ll j=0;j<2*n;j++){
                if(s[j] == -s[i] and !(u[j])){
                    a.push_back({s[j], j});
                    u[j] = true;
                }
            }
        }
    }
    for(ll i=0;i<2*n;i++){
        inv += query(0, 2*n-1, 1, a[i].second, 2*n-1);
        update(0, 2*n-1, 1, a[i].second);
    }
	return inv;
}
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