Submission #682095

#	Time	Username	Problem	Language	Result	Execution time	Memory
682095		sharaelong	Arranging Shoes (IOI19_shoes)	C++17	45 / 100	173 ms	13564 KiB

shoes

#include "shoes.h"

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

struct FenwickTree {
    vector<int> tree;
    FenwickTree(int size) {
        tree.resize(size+1, 0);
    }

    int sum(int pos) {
        int ret = 0;
        for (int i=pos+1; i>0; i &= (i-1)) ret += tree[i];
        return ret;
    }

    void add(int pos, int val) {
        for (int i=pos+1; i<tree.size(); i+=(i & -i)) tree[i] += val;
    }
};

ll inversion_cnt(vector<int> arr) {
    int n = arr.size();
    ll ret = 0;
    FenwickTree fen(n);
    for (int x: arr) {
        ret += fen.sum(n-1) - fen.sum(x);
        fen.add(x, 1);
    }
    sort(arr.begin(), arr.end());
    for (int i=0; i<n; ++i) {
        if (arr[i] != i) assert(false);
    }
    return ret;
}

ll count_swaps(vector<int> s) {
	int n = s.size() / 2;
    vector<vector<int>> arr(n+1);

    int num_cnt = n+1;
    for (int i=0; i<2*n; ++i) arr[abs(s[i])].push_back(i);
    for (int i=1; i<=n; ++i) {
        int pos_cnt = 0, neg_cnt = 0;
        for (int idx: arr[i]) {
            if (s[idx] > 0) {
                s[idx] = num_cnt + pos_cnt;
                pos_cnt++;
            } else {
                s[idx] = -(num_cnt + neg_cnt);
                neg_cnt++;
            }
        }
        num_cnt += pos_cnt;
        assert(pos_cnt == neg_cnt);
    }

    map<int, int> mp;
    for (int i=0; i<s.size(); ++i) {
        if (s[i] < 0) {
            mp[-s[i]] = mp.size();
        }
    }
    assert(mp.size() == n);

    for (int i=0; i<s.size(); ++i) {
        assert(mp.find(abs(s[i])) != mp.end());
        if (s[i] > 0) {
            s[i] = mp[s[i]] * 2 + 1;
        } else {
            s[i] = mp[-s[i]] * 2;
        }
    }
    return inversion_cnt(s);
}

Compilation message (stderr)

shoes.cpp: In member function 'void FenwickTree::add(int, int)':
shoes.cpp:20:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         for (int i=pos+1; i<tree.size(); i+=(i & -i)) tree[i] += val;
      |                           ~^~~~~~~~~~~~
shoes.cpp: In function 'll count_swaps(std::vector<int>)':
shoes.cpp:61:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |     for (int i=0; i<s.size(); ++i) {
      |                   ~^~~~~~~~~
In file included from /usr/include/c++/10/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:33,
                 from shoes.cpp:3:
shoes.cpp:66:22: warning: comparison of integer expressions of different signedness: 'std::map<int, int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   66 |     assert(mp.size() == n);
      |            ~~~~~~~~~~^~~~
shoes.cpp:68:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |     for (int i=0; i<s.size(); ++i) {
      |                   ~^~~~~~~~~

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