arrays - 如何将 iter.next() 转换为数组索引？

Question

我将实现一个数组v来将当前顶点标记为已访问。但是，iter.next() 不能是 LinkedList 的索引或数组的索引。

1. iter.next() 的输出不是整数，而是一个选项 Some。
2. 如何使用Some中的值？如果我使用 Some 中的值作为数组的索引。我应该将值转换为整数吗？

fn bfs(s: usize) {
    let mut cells = vec![LinkedList::<usize>::new(); 4];

    for (i, cell) in cells.iter_mut().enumerate() {
        cell.push_front(i);
    }

    cells[0].push_back(1);
    cells[0].push_back(2);

    cells[1].push_back(2);

    cells[2].push_back(0);
    cells[2].push_back(3);

    cells[3].push_back(3);

    let mut iter = cells[s].iter();
    let mut v = vec![0; 4];

    // Entry point
    for i in 0..cells[s].len() {
        // It is incorrect, "iter.next()" it cannot be a index of LinkedList
        // vector "v" to keep track of which vertex has been traversed
        //v[iter.next()] = 1;
    }
}

fn main() {
    bfs(2);
}

Answer 1

iter.next()返回Option ，你只需要解构它:

for i in 0..cells[s].len() {
    let x = match iter.next() {
        Some(x) => *x,
        None => return,
    };
    v[x] = 1;
}