Submission #364550

#	Time	Username	Problem	Language	Result	Execution time	Memory
364550		tiberiu	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	363 ms	26732 KiB

shoes

#include "shoes.h"
#include <map>
#include <vector>

using namespace std;

const int MAX_N = 200001;
int aib[MAX_N];

void update(int pos, int val) {
    pos++;
    while (pos < MAX_N) {
        aib[pos] += val;
        pos += (pos & -pos);
    }
}

int query(int pos) {
    pos++;
    int ans = 0;
    while (pos) {
        ans += aib[pos];
        pos &= pos - 1;
    }
    return ans;
}

long long count_swaps(std::vector<int> s) {
    map<int, vector<int>> f;

    for (int i = 0; i < s.size(); i++) {
        f[s[i]].push_back(i);
    }

    long long ans = 0;

    vector<int> twin(s.size());
    for (auto x : f) {
        if (x.first < 0)
            continue;

        for (int i = 0; i < f[x.first].size(); i++) {
            twin[f[x.first][i]] = f[-x.first][i];
            twin[f[-x.first][i]] = f[x.first][i];
            if (f[-x.first][i] > f[x.first][i])
                ans++;
        }
    }

    for (int i = 0; i < s.size(); i++) {
        if (twin[i] < i) {
            ans += query(i) - query(twin[i]);
            update(i, 1);
            update(twin[i], 1);
        }
    }

    return ans;
}

Compilation message (stderr)

shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (int i = 0; i < s.size(); i++) {
      |                     ~~^~~~~~~~~~
shoes.cpp:42:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |         for (int i = 0; i < f[x.first].size(); i++) {
      |                         ~~^~~~~~~~~~~~~~~~~~~
shoes.cpp:50:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |     for (int i = 0; i < s.size(); i++) {
      |                     ~~^~~~~~~~~~

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