Submission #661144

#	Time	Username	Problem	Language	Result	Execution time	Memory
661144		amsraman	Arranging Shoes (IOI19_shoes)	C++17	45 / 100	43 ms	10544 KiB

shoes

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

using namespace std;

template <typename T>
struct FenwickTree {
    size_t n;
    vector<T> bit;
    FenwickTree(size_t n): n(n), bit(n, 0) {};
    FenwickTree(vector<T> & init): n((int) init.size()), bit((int) init.size()) {
        copy(init.begin(), init.end(), bit.begin());
        for(int i = 1; i <= n; i++) {
            if(i + (i & -i) <= n) {
                bit[i + (i & -i) - 1] += bit[i - 1];
            }
        }
    }
    T qry(int k) {
        T ret = 0;
        for(k++; k > 0; k -= k & -k) {
            ret += bit[k - 1];
        }
        return ret;
    }
    T qry(int l, int r) {
        return qry(r) - qry(l - 1);
    }
    void upd(int k, T x) {
        for(k++; k <= n; k += k & -k) {
            bit[k - 1] += x;
        }
    }
};

ll count_swaps(vector<int> S) {
    int n = S.size();
    ll ans = 0;
    FenwickTree<ll> ft(n);
    vector<int> lefts;
    vector<vector<int>> rights(n / 2);
    for(int i = 0; i < n; i++) {
        ft.upd(i, 1);
        if(S[i] < 0) {
            lefts.push_back(i);
        } else {
            rights[S[i] - 1].push_back(i);
        }
    }
    for(int i = 0; i < n / 2; i++) {
        reverse(rights[i].begin(), rights[i].end());
    }
    for(int i = 0; i < n / 2; i++) {
        ft.upd(lefts[i], -1); ans += ft.qry(lefts[i]);
        int pos = -S[lefts[i]] - 1, right_back = rights[pos].back(); rights[pos].pop_back();
        ft.upd(right_back, -1); ans += ft.qry(right_back);
    }
    return ans;
}

Compilation message (stderr)

shoes.cpp: In instantiation of 'void FenwickTree<T>::upd(int, T) [with T = long long int]':
shoes.cpp:43:20:   required from here
shoes.cpp:30:20: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   30 |         for(k++; k <= n; k += k & -k) {
      |                  ~~^~~~

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