Submission #2215382

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Source Code Expand

#include <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <typeinfo>
#include <numeric>
#include <functional>
#include <unordered_map>

using namespace std;
using ll = long long;
using ull = unsigned long long;

const ll INF = 1e16;
const ll MOD = 1e9 + 7;

#define REP(i, n) for(int i = 0; i < n; i++)
#define RREP(i, n) for(int i = n - 1; i >= 0; i--)
#define REP2(i, n, k) for(int i = 0; i < n; i += k)



int main() {
    int n, a[100000], b[100000];
    map<int, int> m;
    
    cin >> n;
    REP(i, n){
        cin >> a[i];
        b[i] = a[i];
    }
    
    sort(b, b + n);
    REP(i, n){
        m[b[i]] = i;
    }
    
    int ans = 0;
    REP(i, n){
        if(i % 2 != m[a[i]] % 2){
            ans++;
        }
    }
    
    cout << ans / 2 << endl;
}

Submission Info

Judge Result