How to initialize a vector of usize with a dummy value?

#1

Hi all,

In my program I want to save the index values of a vector (u) in some other vector (v). But this
I want this vector (v) initialized with -1. So that I can compare with to know when to stop it.

I am doing

let v = vec![1, 2, 3];
let mut u = vec![-1, -1, -1];
u[0] = 2;
println!("{}", v[u[0]]);

This doesn't work.

I know that u has to be of usize, and it doesn't support negative values. Is there any other way to do it?
Or are there any dummy values to initialize the usize vector?

#2

How about usize::max_value()

#3

The main algorithm goes as

// some random vector
let v = vec![1., 3., 5., 2.3, 22., 0., 9.];
// vector holding the indices of vector v (with some condition)
let u = vec![4, 3, 5, 2, 1, -1, -1];
let indices = vec![];
let mut next = 0;
while next != -1 {
    indices.append(next);
    next = u[next];
}

The result will be

indices = vec![0, 4, 1, 3, 2, 5];

I see that usize::max_value works, just in case can I have some other solution, provided the above algorithm.

#4

Could you use an Option<usize> for this?

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