Submission #845312

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Source Code Expand

#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N; cin >> N;
	vector<int> a(N);
	for (int& x: a) cin >> x;
	vector<int> A = a;
	sort(A.begin(), A.end());
	for (int& x: a) x = lower_bound(A.begin(), A.end(), x) - A.begin();
	int ans = 0;
	for (int i = 0; i < N; i++)
		if (i % 2 != a[i] % 2)
			ans++;
	cout << ans / 2 << endl;
}

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