#include <bits/stdc++.h>
#include "shoes.h"
using namespace std;
const int MAXN = 200005;
int n;
vector<pair<int, int>> same_size[MAXN];
vector<pair<int, int>> matchings;
struct FenwickTree {
int fenwick[MAXN];
void update(int pos, int val) {
while (pos < 2 * n) {
fenwick[pos] += val;
pos += (pos & (-pos));
}
}
int query(int pos) {
int result = 0;
while (pos > 0) {
result += fenwick[pos];
pos -= (pos & (-pos));
}
return result;
}
};
FenwickTree Fenwick;
long long count_swaps(const vector<int>& shoes) {
n = int(shoes.size()) / 2;
for (int i = 0; i < 2 * n; i++) {
same_size[abs(shoes[i])].push_back({shoes[i], i});
}
long long ans = 0;
for (int i = 1; i <= n; i++) {
sort(same_size[i].begin(), same_size[i].end());
for (int j = 0; j < int(same_size[i].size()) / 2; j++) {
int l = same_size[i][j].second;
int r = same_size[i][j + same_size[i].size() / 2].second;
if (l > r) {
swap(l, r);
ans++;
}
matchings.push_back({l + 1, r + 1});
}
}
sort(matchings.begin(), matchings.end());
for (int i = 1; i <= 2 * n; i++) Fenwick.update(i, 1);
for (auto [l, r] : matchings) {
if (r - l > 1) ans += Fenwick.query(r - 1) - Fenwick.query(l);
Fenwick.update(l, -1);
Fenwick.update(r, -1);
}
return ans;
}
Compilation message
shoes.cpp: In function 'long long int count_swaps(const std::vector<int>&)':
shoes.cpp:65:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
65 | for (auto [l, r] : matchings) {
| ^
/usr/bin/ld: /tmp/ccQack41.o: in function `main':
grader.cpp:(.text.startup+0x29d): undefined reference to `count_swaps(std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status