Submission #1594783

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double 
#define vpi vector<pair <int, int> >
#define vi vector<int>
#define vl vector<ll>
#define vpl vector<pair<ll, ll> >
#define pb push_back
#define mp make_pair
#define all(p) (p).begin(), (p).end()
#define fi first
#define se second
#define mem(a) memset(a, 0 , sizeof(a))
#define mod 1e9+7
#define inf 100000000007
#define N 100002
vi a(N);

int main(){
	ios_base::sync_with_stdio(NULL),cin.tie(NULL),cout.tie(NULL);
	int n, ma=0;
	cin >> n;
	
	for (int i = 1; i <= n; ++i) {
		cin >> a[i];
	}

	if(a[1] == 1){
		a[2] += a[1];
		a[1] = a[2] - a[1];
		a[2] -= a[1];
		ma++;
	}
	for(int i = 2; i < n; ++i) {
		if(a[i] == i) {
			ma++;
			if(a[i+1] != i) {
				a[i+1] += a[i];
				a[i] = a[i+1] - a[i];
				a[i+1] -= a[i];
			}
			else {
				a[i] += a[i-1];
				a[i-1] = a[i] - a[i-1];
				a[i] -= a[i-1];
			}
		}
	}
	if(a[n] == n) {
		ma++;
		a[n] += a[n-1];
		a[n-1] = a[n] - a[n-1];
		a[n] -= a[n-1];

	}

	cout << ma << "\n";
	return 0;
}

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