Submission #1777544

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Source Code Expand

use std::io;

fn next_int() -> i64 {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.trim().parse().unwrap()
}

fn next_vec() -> Vec<i64> {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.split_whitespace().map(|n| n.parse().unwrap()).collect()
}

fn main() {
    let n = next_int();
    let a = next_vec();

    let mut cnt = 0;

    for i in 0..n {
        let idx = i as usize;
        let idx2 = a[idx] as usize;
        cnt += if a[idx2-1] == i + 1 {1} else {0};
    }

    println!("{:?}", cnt/2);
}

Submission Info

Judge Result