Submission #835830

#	Time	Username	Problem	Language	Result	Execution time	Memory
835830		kamelfanger83	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	207 ms	15684 KiB

shoes

#include <iostream>
#include <vector>
#include <set>
#include <cassert>

#include "shoes.h"

using namespace std;

struct Segtree{
    vector<int> cache;
    Segtree (int n){
        cache.resize(4 * n);
    }
    int update(int l, int r, int i, int ui, int ux){
        if(ui < l || r <= ui) return cache[i];
        if (l + 1 == r) return cache[i] = ux;
        int m = l + (r-l)/2;
        return cache[i] = update(l, m, i*2+1, ui, ux) + update(m, r, i*2+2, ui, ux);
    }
    int query(int l, int r, int i, int ql, int qr){
        if (qr <= l || r <= ql) return 0;
        if (ql <= l && r <= qr) return cache[i];
        int m = l + (r-l)/2;
        return query(l, m, i*2+1, ql, qr) + query(m, r, i*2+2, ql, qr);
    }
};

long long count_swaps(vector<int> S){
    set<pair<int, int>> lefts, rights;
    for (int ii = 0; ii < S.size(); ++ii) {
        int i = S[ii];
        if (i < 0) lefts.insert({-i, ii});
        else rights.insert({i, ii});
    }
    int n = S.size();
    Segtree segtree (n);
    long long ans = 0;
    vector<bool> free (n, true);
    for (int i = 0; i < n; ++i) {
        if (!free[i]) {
            continue;
        }
        int left, right;
        if (S[i] < 0) {
            left = i;
            right = rights.lower_bound({-S[i], 0})->second;
        }
        else {
            right = i;
            left = lefts.lower_bound({S[i], 0})->second;
        }
        int f1, f2;
        lefts.erase({abs(S[i]), left});
        rights.erase({abs(S[i]), right});
        ans += f1 = left - segtree.query(0, n, 0, 0, left);
        segtree.update(0, n, 0, left, 1);
        ans += f2 = right - segtree.query(0, n, 0, 0, right);
        assert(f1 == 0 || f2 == 0);
        segtree.update(0, n, 0, right, 1);
        free[left] = free[right] = false;
    }
    return ans;
}
/*
int main(){
    cout << count_swaps({2, 2, 2, -2, -2, -2}) ;
}*/

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:31:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (int ii = 0; ii < S.size(); ++ii) {
      |                      ~~~^~~~~~~~~~

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