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// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0
#[derive(Debug)]
struct Point(i32, i32);

/// 在 `points` 中搜索最接近 `query` 的点。
/// 假定 `points` 中至少有一个点。
fn find_nearest<'a>(points: &'a [Point], query: &Point) -> &'a Point {
    fn cab_distance(p1: &Point, p2: &Point) -> i32 {
        (p1.0 - p2.0).abs() + (p1.1 - p2.1).abs()
    }

    let mut nearest = None;
    for p in points {
        if let Some((_, nearest_dist)) = nearest {
            let dist = cab_distance(p, query);
            if dist < nearest_dist {
                nearest = Some((p, dist));
            }
        } else {
            nearest = Some((p, cab_distance(p, query)));
        };
    }

    nearest.map(|(p, _)| p).unwrap()
    // query // What happens if we do this instead?
}

fn main() {
    let points = &[Point(1, 0), Point(1, 0), Point(-1, 0), Point(0, -1)];
    let query = Point(0, 2);
    let nearest = find_nearest(points, &query);

    // 此时 `query` 未被借用。
    drop(query);

    dbg!(nearest);
}