Submission #797494

#	Time	Username	Problem	Language	Result	Execution time	Memory
797494		Liudas	Arranging Shoes (IOI19_shoes)	C++17	100 / 100	665 ms	157324 KiB

shoes

#include <bits/stdc++.h>
using namespace std;
struct fenwick_tree{
    vector<int> tree;
    fenwick_tree(int N){
        tree.assign(N + 5, 0);
        for(int i = 1; i <= N; i ++){
            for(int j = i; j < tree.size(); j += (j & -j)){
                tree[j] ++;
            }
        }
    }
    void rem(int p){
        for(int i = p; i < tree.size(); i += (i & -i)){
            tree[i]--;
        }
    }
    int sum(int p){
        int s = 0;
        for(int i = p; i > 0; i -= (i & -i)){
            s += tree[i];
        }
        return s;
    }
};
long long count_swaps(vector<int> S){
    long long N = S.size();
    fenwick_tree tree(N);
    map<int, queue<int>> arr;
    set<int> left;
    long long ans = 0;
    for(int i = 0; i < N; i ++){
        left.insert(i);
        arr[S[i]].push(i);
    }
    for(int i = 0; i < N / 2; i ++){
        int s = *left.begin();
        left.erase(s);
        int b = arr[-S[s]].front();
        left.erase(b);
        arr[S[s]].pop();
        arr[-S[s]].pop();
        if(S[s] > 0){
            ans += tree.sum(b+1) - tree.sum(s+1);
        }
        else{
            ans += tree.sum(b+1) - tree.sum(s+1) - 1;
        }
        tree.rem(s+1);
        tree.rem(b+1);
    }
    return ans;
}

Compilation message (stderr)

shoes.cpp: In constructor 'fenwick_tree::fenwick_tree(int)':
shoes.cpp:8:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 |             for(int j = i; j < tree.size(); j += (j & -j)){
      |                            ~~^~~~~~~~~~~~~
shoes.cpp: In member function 'void fenwick_tree::rem(int)':
shoes.cpp:14:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |         for(int i = p; i < tree.size(); i += (i & -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