Segment Tree of Placements

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The pstree crate allows you to create an n to k segment tree of placements based on a key in the range 0..=n. This key will be used as the root and leaves of the tree. So other vertices will be taken in the ranges 0..key and key + 1..=n.

The structure is designed to quickly respond to queries to change a vertex or edge in a weighted directed graph that allows edges of negative weight.

Example

use pstree::PSTree;

fn main() {
    let pstree = PSTree::new(3, 2, 0, 0);
    let _shortest = pstree.update_vertex(1, 1);
    let _shortest = pstree.update_edge(0, 1, 2);
}

The PSTree::new(3, 2, 0, 0) creates a 3 by 2 tree of placements based on key 0 with initial value 0:

0
├── 1
│   ├── 2
│   │   └── 0
│   └── 3
│       └── 0
├── 2
│   ├── 1
│   │   └── 0
│   └── 3
│       └── 0
└── 3
    ├── 1
    │   └── 0
    └── 2
        └── 0

The pstree.update_vertex(1, 1) updates vertex 1 with value 1, so the distances will be recalculated, returning the shortest distance from key of length k:

0
├── 1
│   '-- 2
│   '   '-- 0
│   '-- 3
│       '-- 0
├── 2
│   ├── 1
│   │   '-- 0
│   └── 3
│       └── 0
└── 3
    ├── 1
    │   '-- 0
    └── 2
        └── 0

The pstree.update_edge(0, 1, 2) updates edge from 0 to 1 with value 2, so the distances will be recalculated, returning the shortest distance from key of length k:

0
'-- 1
│   '-- 2
│   '   '-- 0
│   '-- 3
│       '-- 0
├── 2
│   ├── 1
│   │   └── 0
│   └── 3
│       └── 0
└── 3
    ├── 1
    │   └── 0
    └── 2
        └── 0

Usage

[dependencies]
pstree = "0.1"

License

Licensed under either of

• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

at your option.