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use std::io::{self, Read};
#[derive(Clone, Copy)]
struct Elf {
gifts: usize,
next: usize,
}
fn solve(count: usize) -> usize {
let mut circle: Vec<Elf> = (0..count).map(|i| Elf { gifts: 1, next: i + 1 }).collect();
circle.last_mut().unwrap().next = 0;
let mut index = 0;
while circle[index].gifts < count {
let next = circle[index].next;
circle[index].gifts += circle[next].gifts;
circle[next].gifts = 0;
circle[index].next = circle[next].next;
index = circle[index].next;
}
index + 1
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve(input.trim().parse().unwrap()));
}
#[test]
fn part1() {
assert_eq!(3, solve(5));
}
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