CF#201 div2 B Fixed Points(implementation)

地址

题意

解析

代码

#pragma comment(linker, "/STACK:1677721600")
#include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <cassert>
#include <iostream>
#include <algorithm>
#define pb push_back
#define mp make_pair
#define LL long long
#define lson lo,mi,rt<<1
#define rson mi+1,hi,rt<<1|1
#define Min(a,b) ((a)<(b)?(a):(b))
#define Max(a,b) ((a)>(b)?(a):(b))
#define mem(a,b) memset(a,b,sizeof(a))
#define FIN freopen("in.txt", "r", stdin)
#define FOUT freopen("out.txt", "w", stdout)
#define rep(i,a,b) for(int i=(a); i<=(b); i++)
#define dec(i,a,b) for(int i=(a); i>=(b); i--)

using namespace std;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double ee = exp(1.0);
const int inf = 0x3f3f3f3f;
const int maxn = 1e6 + 10;
const double pi = acos(-1.0);

int readT()
{
char c;
int ret = 0,flg = 0;
while(c = getchar(), (c < '0' || c > '9') && c != '-');
if(c == '-') flg = 1; else ret = c ^ 48;
while( c = getchar(), c >= '0' && c <= '9') ret = ret * 10 + (c ^ 48);
return flg ? - ret : ret;
}

LL readTL()
{
char c;
int flg = 0;
LL ret = 0;
while(c = getchar(), (c < '0' || c > '9') && c != '-');
if(c == '-') flg = 1; else ret = c ^ 48;
while( c = getchar(), c >= '0' && c <= '9') ret = ret * 10 + (c ^ 48);
return flg ? - ret : ret;
}

int a[maxn];

int main()
{
#ifdef LOCAL
FIN;
#endif // LOCAL
int n = readT();
int ans = 0;
rep(i, 0, n - 1)
{
a[i] = readT();
if (a[i] == i)
{
ans++;
}
}

if (ans == n)
{
printf("%d\n", ans);
return 0;
}

rep(i, 0, n - 1)
{
if (a[i] == i)
continue;
if (i == a[a[i]])
{
printf("%d\n", ans + 2);
return 0;
}
}

printf("%d\n", ans + 1);

return 0;
}