Submission #845404

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ii, ii> iii;
ll MOD = 1e9 + 7;
const ld E = 1e-7;
#define null NULL
#define ms(x) memset(x, 0, sizeof(x))
#ifndef LOCAL
#define endl "\n"
#endif
#define sync ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define _read(x) freopen(x, "r", stdin)
#define _write(x) freopen(x, "w", stdout)
#define files(x) _read(x ".in"); _write(x ".out")
#define filesdatsol(x) _read(x ".DAT"); _write(x ".SOL")
#define output _write("output.txt")
#define input _read("input.txt")
#define mod % MOD
#define y1 hello_world
unsigned char ccc;
bool _minus = false;
template<typename T>
inline T sqr(T t) {
	return (t * t);
}
inline void read(ll &n) {
	n = 0;
	_minus = false;
	while (true) {
		ccc = getchar();
		if (ccc == ' ' || ccc == '\n')
			break;
		if (ccc == '-') {
			_minus = true;
			continue;
		}
		n = n * 10 + ccc - '0';
	}
	if (_minus)
		n *= -1;
}
inline void read(int &n) {
	n = 0;
	_minus = false;
	while (true) {
		ccc = getchar();
		if (ccc == ' ' || ccc == '\n')
			break;
		if (ccc == '-') {
			_minus = true;
			continue;
		}
		n = n * 10 + ccc - '0';
	}
	if (_minus)
		n *= -1;
}
char wwww[19];
int kkkk;
inline void write(ll y) {
	long long x = y;
	kkkk = 0;
	if (!x)
		++kkkk, wwww[kkkk] = '0';
	else
		while (x) {
			++kkkk;
			wwww[kkkk] = char(x % 10 + '0');
			x /= 10;
		}
	for (int i = kkkk; i >= 1; --i)
		putchar(wwww[i]);
	putchar('\n');
}

#ifdef LOCAL
//#define DEBUG
#endif


int main() {
	srand(time(NULL));
	cout.precision(10);
	cout << fixed;
	sync;
#ifdef LOCAL
	input;
#else

#endif

	int n;
	cin >> n;
	vector<ii> v;
	for(int i = 0; i < n; i++){
		int a;
		cin >> a;
		v.push_back(make_pair(a, i));
	}
	sort(v.begin(), v.end());
	int ans = 0;
	for(int i = 0; i < n; i++){
		if(i % 2 != v[i].second % 2)
			ans++;
	}
	assert(ans % 2 == 0);
	ans /= 2;
	cout << ans << endl;
}

Submission Info

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