Submission #420458

#	Time	Username	Problem	Language	Result	Execution time	Memory
420458		QCFium	Arranging Shoes (IOI19_shoes)	C++14	100 / 100	436 ms	27172 KiB

shoes

#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}

struct SegTree {
	int n;
	std::vector<int> data;
	SegTree (int n_) {
		for (n = 1; n < n_; n <<= 1);
		data.resize(n << 1);
		for (int i = 0; i < n_; i++) data[i + n] = 1;
		for (int i = n; --i; ) data[i] = data[i << 1] + data[i << 1 | 1];
	}
	void add(int i, int val) {
		for (i += n; i; i >>= 1) data[i] += val;
	}
	int sum(int l, int r) {
		int res = 0;
		for (l += n, r += n; l < r; l >>= 1, r >>= 1) {
			if (r & 1) res += data[--r];
			if (l & 1) res += data[l++];
		}
		return res;
	}
};

long long count_swaps(std::vector<int> a) {
	int n = a.size();
	
	std::map<int, std::vector<int> > index;
	for (int i = 0; i < n; i++) index[a[i]].push_back(i);
	for (auto &i : index) std::reverse(i.second.begin(), i.second.end());
	
	SegTree tree(n);
	std::vector<bool> alive(n, true);
	int64_t res = 0;
	for (int i = 0; i < n; i++) {
		if (!alive[i]) continue;
		int t = index[-a[i]].back();
		index[-a[i]].pop_back();
		index[a[i]].pop_back();
		alive[i] = false;
		alive[t] = false;
		tree.add(i, -1);
		tree.add(t, -1);
		res += tree.sum(i, t);
		if (a[i] > 0) res++;
	}
	return res;
}

Compilation message (stderr)

shoes.cpp: In function 'int ri()':
shoes.cpp:5:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
    5 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~

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