Rust (#190)

Add Rust implementation of some algorithms

.github/workflows/rust.yml

@@ -0,0 +1,20 @@
+name: Rust CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build-ubuntu-rustc:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: install rustc
+        run: |
+          sudo apt install rustc
+      - name: compile
+        run: |
+          cd rust
+          cargo

README.md

@@ -3,7 +3,7 @@
 [![C++ CI](https://github.com/indy256/codelibrary/actions/workflows/cpp.yml/badge.svg)](https://github.com/indy256/codelibrary/actions/workflows/cpp.yml)
 [![License](https://img.shields.io/badge/license-UNLICENSE-green.svg)](https://github.com/indy256/codelibrary/blob/master/UNLICENSE)
 
-### Collection of algorithms and data structures in C++, Java, Kotlin and Python
+### Collection of algorithms and data structures in C++, Java, Kotlin, Python and Rust
 
 #### Data structures
 + [x] Segment tree [**c++**](cpp/structures/segment_tree.h) [**java**](java/structures/SegmentTree.java) [**kotlin**](kotlin/SegmentTree.kt)

rust/.gitignore

@@ -0,0 +1,4 @@
+.idea
+*.iml
+Cargo.lock
+target

rust/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "codelibrary"
+version = "0.1.0"
+
+edition = "2018"
+
+[[bin]]
+name = "topological_sort"
+path = "graphs/dfs/topological_sort.rs"
+
+[[bin]]
+name = "dijkstra"
+path = "graphs/shortestpaths/dijkstra.rs"
+
+[[bin]]
+name = "max_bipartite_matching_EV"
+path = "graphs/matchings/max_bipartite_matching_EV.rs"
+
+[[bin]]
+name = "euclid"
+path = "numbertheory/euclid.rs"
+
+[[bin]]
+name = "disjoint_sets"
+path = "structures/disjoint_sets.rs"
+
+[[bin]]
+name = "fenwick_tree"
+path = "structures/fenwick_tree.rs"

rust/graphs/dfs/topological_sort.rs

@@ -0,0 +1,28 @@
+fn dfs(graph: &Vec<Vec<usize>>, used: &mut Vec<bool>, order: &mut Vec<usize>, u: usize) {
+    used[u] = true;
+    for v in &graph[u] {
+        if !used[*v] {
+            dfs(graph, used, order, *v);
+        }
+    }
+    order.push(u);
+}
+
+pub fn topological_sort(graph: &Vec<Vec<usize>>) -> Vec<usize> {
+    let n = graph.len();
+    let mut used = vec![false; n];
+    let mut order = Vec::<usize>::new();
+    for i in 0..n {
+        if !used[i] {
+            dfs(graph, &mut used, &mut order, i);
+        }
+    }
+    order.reverse();
+    return order;
+}
+
+fn main() {
+    let g = vec![vec![0], vec![], vec![0, 1]];
+    let order = topological_sort(&g);
+    assert_eq!(order, vec![2, 1, 0]);
+}

rust/graphs/matchings/max_bipartite_matching_EV.rs

@@ -0,0 +1,31 @@
+fn find_path(graph: &Vec<Vec<usize>>, u1: usize, matching: &mut Vec<usize>, vis: &mut Vec<bool>) -> bool {
+    vis[u1] = true;
+    for v in &graph[u1] {
+        let u2 = matching[*v];
+        if u2 == usize::MAX || (!vis[u2] && find_path(graph, u2, matching, vis)) {
+            matching[*v] = u1;
+            return true;
+        }
+    }
+    return false;
+}
+
+pub fn max_matching(graph: &Vec<Vec<usize>>, n2: usize) -> (usize, Vec<usize>) {
+    let n1 = graph.len();
+    let mut matching = vec![usize::MAX; n2];
+    let mut matches = 0;
+    for u in 0..n1 {
+        let mut vis = vec![false; n1];
+        if find_path(graph, u, &mut matching, &mut vis) {
+            matches += 1;
+        }
+    }
+    return (matches, matching);
+}
+
+fn main() {
+    let g = vec![vec![0, 1], vec![0]];
+    let (cardinality, matching) = max_matching(&g, 2);
+    assert_eq!(cardinality, 2);
+    assert_eq!(matching, vec![1, 0]);
+}

rust/graphs/shortestpaths/dijkstra.rs

@@ -0,0 +1,31 @@
+use std::collections::BinaryHeap;
+
+// https://cp-algorithms.com/graph/dijkstra_sparse.html
+// O(E*log(V)) time and O(E) memory
+pub fn dijkstra_heap(graph: &Vec<Vec<(usize, i32)>>, s: usize) -> (Vec<i32>, Vec<usize>) {
+    let n = graph.len();
+    let mut prio = vec![i32::MAX; n];
+    let mut pred = vec![usize::MAX; n];
+    let mut q = BinaryHeap::<(i32, usize)>::new();
+    prio[s] = 0;
+    q.push((0, s));
+    while let Some((d, u)) = q.pop() {
+        if -d != prio[u] { continue; }
+        for (v, len) in &graph[u] {
+            let nprio = prio[u] + len;
+            if prio[*v] > nprio {
+                prio[*v] = nprio;
+                pred[*v] = u;
+                q.push((-nprio, *v));
+            }
+        }
+    }
+    return (prio, pred);
+}
+
+fn main() {
+    let g = vec![vec![(1, 10), (2, 8)], vec![(2, -5)], vec![]];
+    let (prio, pred) = dijkstra_heap(&g, 0);
+    assert_eq!(prio, vec![0, 10, 5]);
+    assert_eq!(pred, vec![usize::MAX, 0, 1]);
+}

rust/numbertheory/euclid.rs

@@ -0,0 +1,30 @@
+fn gcd(a: i32, b: i32) -> i32 {
+    return if b == 0 { a.abs() } else { gcd(b, a % b) };
+}
+
+// returns { gcd(a,b), x, y } such that gcd(a,b) = a*x + b*y
+fn euclid(mut a: i64, mut b: i64) -> [i64; 3] {
+    let mut x: i64 = 1;
+    let mut y: i64 = 0;
+    let mut x1: i64 = 0;
+    let mut y1: i64 = 1;
+    // invariant: a=a_orig*x+b_orig*y, b=a_orig*x1+b_orig*y1
+    while b != 0 {
+        let q = a / b;
+        let _x1 = x1;
+        let _y1 = y1;
+        let _b = b;
+        x1 = x - q * x1;
+        y1 = y - q * y1;
+        b = a - q * b;
+        x = _x1;
+        y = _y1;
+        a = _b;
+    }
+    return if a > 0 { [a, x, y] } else { [-a, -x, -y] };
+}
+
+fn main() {
+    assert_eq!(gcd(15, 20), 5);
+    assert_eq!(euclid(6, 9), [3, -1, 1]);
+}

rust/structures/disjoint_sets.rs

@@ -0,0 +1,30 @@
+struct DisjointSets {
+    p: Vec<usize>
+}
+
+impl DisjointSets {
+    pub fn new(n: usize) -> Self {
+        DisjointSets { p: (0..n).collect() }
+    }
+
+    pub fn root(&mut self, x: usize) -> usize {
+        if x != self.p[x] {
+            self.p[x] = self.root(self.p[x]);
+        }
+        self.p[x]
+    }
+
+    pub fn unite(&mut self, a: usize, b: usize) {
+        let a = self.root(a);
+        let b = self.root(b);
+        self.p[b] = a;
+    }
+}
+
+fn main() {
+    let mut ds = DisjointSets::new(3);
+    ds.unite(0, 2);
+    assert_eq!(ds.root(0), 0);
+    assert_eq!(ds.root(1), 1);
+    assert_eq!(ds.root(2), 0);
+}

rust/structures/fenwick_tree.rs

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+use std::ops::AddAssign;
+
+struct Fenwick<T> {
+    t: Vec<T>
+}
+
+impl<T: AddAssign + Copy + From<i32>> Fenwick<T> {
+    fn new(n: usize) -> Self {
+        Fenwick { t: vec![0.into(); n] }
+    }
+
+    pub fn add(&mut self, mut i: usize, value: T) {
+        while i < self.t.len() {
+            self.t[i] += value;
+            i |= i + 1;
+        }
+    }
+
+    // sum[0..i]
+    pub fn sum(&self, mut i: i32) -> T {
+        let mut res: T = 0.into();
+        while i >= 0 {
+            res += self.t[i as usize];
+            i = (i & (i + 1)) - 1;
+        }
+        return res;
+    }
+}
+
+fn main() {
+    let mut t = Fenwick::<i32>::new(3);
+    t.add(0, 4);
+    t.add(1, 5);
+    t.add(2, 5);
+    t.add(2, 5);
+    assert_eq!(t.sum(0), 4);
+    assert_eq!(t.sum(2), 19);
+}