Submission #1017568

#	Time	Username	Problem	Language	Result	Execution time	Memory
1017568		c2zi6	Arranging Shoes (IOI19_shoes)	C++14	50 / 100	1094 ms	31476 KiB

shoes

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<class T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#include "shoes.h"

struct BIT {
    VL a;
    BIT(int sz) {
        // indexes are [1, sz]
        a = VL(sz+1);
    }
    void add(int i) {
        while (i < a.size()) a[i]++, i += i&-i;
    }
    int get(int i) {
        int ret = 0;
        while (i) ret += a[i], i -= i&-i;
        return ret;
    }
};

ll inversions(VI a) {
    // a is a permutation
    int n = a.size();
    BIT bit(n);
    ll ret = 0;
    rep(i, n) {
        ret += i-bit.get(a[i]+1);
        bit.add(a[i]+1);
    }
    return ret;
}

ll distance(VI a, VI b) {
    int n = a.size();
    VI p;
    map<int, VI> mp;
    reprl(i, n-1, 0) {
        mp[b[i]].pb(i);
    }
    for (int x : a) {
        p.pb(mp[x].back());
        mp[x].pop_back();
    }
    return inversions(p);
}

ll count_swaps(VI s) {
    int n = s.size()/2;
    VI shoes;
    for (int x : s) if (x > 0) shoes.pb(x);
    sort(all(shoes));
    ll ans = 1e18;
    do {
        VI wbe;
        for (int x : shoes) {
            wbe.pb(-x);
            wbe.pb(+x);
        }
        setmin(ans, distance(s, wbe));
    } while (next_permutation(all(shoes)));
	return ans;
}

Compilation message (stderr)

shoes.cpp: In member function 'void BIT::add(int)':
shoes.cpp:41:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |         while (i < a.size()) a[i]++, i += i&-i;
      |                ~~^~~~~~~~~~
shoes.cpp: In function 'll count_swaps(VI)':
shoes.cpp:77:9: warning: unused variable 'n' [-Wunused-variable]
   77 |     int n = s.size()/2;
      |         ^

• Subtask 1: 10 / 10
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 15