Implemented generation of all anagrams (permutations / substitutions)

Cargo.toml

@@ -7,6 +7,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+bit_field = "0.10.1"
 crunchy = "0.2.2"
 packed_simd = { version = "0.3.4", package = "packed_simd_2", features = ["into_bits"] }
 permutohedron = "0.2.4"

README.md

@@ -21,7 +21,7 @@ which produce given MD5 hashes.
 in the dictionary; and it makes the total number of anagrams astronomically large)
 
 This is a working draft, so far the code is extremely dirty (this is my first Rust project),
-and it only lists all anagrams (not including words reordering)
+and it only lists all anagrams
 and does not yet do actual MD5 calculation.
 
 ## Algorithm description

src/anagram_finder.rs

@@ -15,9 +15,10 @@ fn find_anagrams_recursive(remainder: &vector_alphabet::Vector, remaining_depth:
         .take_while(|(_, vector)| vector.norm * remaining_depth >= remainder.norm)
         .map(|(index, vector)| match remainder.safe_substract(&vector) {
             Some(new_remainder) => find_anagrams_recursive(&new_remainder, remaining_depth-1, word_vectors, index)
-                .iter()
-                .map(|partial_phrase| {
-                    vec![index].iter().chain(partial_phrase).cloned().collect()
+                .into_iter()
+                .map(|mut partial_phrase| {
+                    partial_phrase.push(index);
+                    partial_phrase
                 })
                 .collect(),
             _ => vec![],

src/anagram_logger.rs

@@ -1,6 +1,8 @@
-use crate::dictionary_builder;
+use crate::dictionary_builder::Dictionary;
+use crate::dictionary_builder::WordInfo;
+use crate::permutations_cache::PermutationsCache;
 
-pub fn get_anagram_view(anagram: Vec<usize>, dictionary: &dictionary_builder::Dictionary) -> String {
+pub fn get_anagram_view(anagram: &Vec<usize>, dictionary: &Dictionary) -> String {
     anagram.iter()
         .map(|&index| {
             let word_options = &dictionary.words[index];
@@ -13,3 +15,41 @@ pub fn get_anagram_view(anagram: Vec<usize>, dictionary: &dictionary_builder::Di
         .collect::<Vec<_>>()
         .join(" ")
 }
+
+fn generate_substitutions<T: Copy>(simple_dictionary: &[Vec<T>], remaining_length: usize) -> Vec<Vec<T>> {
+    if remaining_length == 0 {
+        return vec![Vec::new()];
+    }
+
+    return simple_dictionary[remaining_length - 1].iter()
+        .flat_map(|&value| {
+            generate_substitutions(simple_dictionary, remaining_length - 1).into_iter()
+                .map(move |mut partial_substitution| {
+                    partial_substitution.push(value);
+                    partial_substitution
+                })
+        })
+        .collect();
+}
+
+pub fn log_anagrams(anagram_vector: &Vec<usize>, dictionary: &Dictionary, permutations: &PermutationsCache) -> () {
+    let simple_vector: Vec<usize> = (0..anagram_vector.len()).collect();
+    let simple_dictionary: Vec<Vec<&WordInfo>> = (0..anagram_vector.len())
+        .map(|i| dictionary.words[anagram_vector[i]].iter().map(|word_info| word_info).collect())
+        .collect();
+    let substitutions: Vec<Vec<&WordInfo>> = generate_substitutions::<&WordInfo>(&simple_dictionary, simple_dictionary.len());
+
+    permutations.get_permuted_vectors(&simple_vector).iter()
+        .flat_map(|permuted_vector| {
+            substitutions.iter().map(move |substitution| {
+                permuted_vector.iter().map(|&index| substitution[index]).collect::<Vec<_>>()
+            })
+        })
+        .for_each(|anagram| {
+            let phrase = anagram.iter()
+                .map(|word_info| word_info.word.clone())
+                .collect::<Vec<_>>()
+                .join(" ");
+            println!("{}", phrase);
+        })
+}

src/lib.rs

@@ -4,6 +4,7 @@ pub mod anagram_finder;
 pub mod anagram_logger;
 pub mod dictionary_builder;
 pub mod hash_computer;
+pub mod permutation_type;
 pub mod permutations_cache;
 pub mod read_lines;
 pub mod vector_alphabet;

src/main.rs

@@ -8,6 +8,7 @@ use trustpilot_challenge_rust::anagram_finder;
 use trustpilot_challenge_rust::anagram_logger;
 use trustpilot_challenge_rust::dictionary_builder;
 use trustpilot_challenge_rust::hash_computer;
+use trustpilot_challenge_rust::permutations_cache;
 use trustpilot_challenge_rust::read_lines;
 
 fn main() {
@@ -39,9 +40,11 @@ fn main() {
 
     let dictionary = dictionary_builder::build_dictionary(phrase, words);
 
-    for number_of_words in 0..=max_number_of_words {
+    for number_of_words in 1..=max_number_of_words {
+        //println!("======= Number of words: {} =======", number_of_words);
+        let permutations = permutations_cache::PermutationsCache::new(number_of_words);
         let result = anagram_finder::find_anagrams(&dictionary, number_of_words);
-        result.into_par_iter()
-            .for_each(|anagram| println!("{}", anagram_logger::get_anagram_view(anagram, &dictionary)));
+        result.par_iter()
+            .for_each(|anagram_vector| anagram_logger::log_anagrams(anagram_vector, &dictionary, &permutations));
     }
 }

src/permutation_type.rs

@@ -0,0 +1,42 @@
+use bit_field::BitField;
+
+// permutation type is a bit field,
+// 1 at i-th position means that in the permutation,
+// value i must occur earlier than the value i+1
+
+// For a given ordered vector (similar to what vec.dedup needs - that is,
+// matching values only appear next to each other),
+// it should return a permutation type with 1 in position of all values
+// which are equal to the next values,
+// so that all permutations of this type applied to the vector
+// will produce all unique permutations of its values
+pub fn get_required_permutation_type<T: Eq>(ordered_vector_to_permute: &[T]) -> u16 {
+    let mut result: u16 = 0;
+    for i in 0..(ordered_vector_to_permute.len() - 1) {
+        if ordered_vector_to_permute[i] == ordered_vector_to_permute[i+1] {
+            result.set_bit(i, true);
+        }
+    }
+
+    result
+}
+
+pub fn get_supported_permutation_types(inverse_permutation: &[usize]) -> Vec<u16> {
+    assert!(inverse_permutation.len() <= 16);
+
+    let mut max_supported_type: u16 = 0;
+    for i in 0..(inverse_permutation.len()-1) {
+        if inverse_permutation[i] < inverse_permutation[i+1] {
+            max_supported_type.set_bit(i, true);
+        }
+    }
+
+    let mut supported_types: Vec<u16> = Vec::new();
+    for i in 0..=u16::MAX {
+        if (i & max_supported_type) == i {
+            supported_types.push(i);
+        }
+    }
+
+    supported_types
+}

src/permutations_cache.rs

@@ -1 +1,58 @@
 use permutohedron::Heap;
+use crate::permutation_type::get_required_permutation_type;
+use crate::permutation_type::get_supported_permutation_types;
+
+pub struct PermutationsCache {
+    permutations_by_type: Vec<Vec<Vec<usize>>>,
+    set_length: usize,
+}
+
+fn invert_permutation(permutation: &Vec<usize>) -> Vec<usize> {
+    let mut result = permutation.clone();
+    for i in 0..permutation.len() {
+        result[permutation[i]] = i;
+    }
+
+    result
+}
+
+impl PermutationsCache {
+    pub fn new(set_length: usize) -> PermutationsCache {
+        assert!(set_length <= 16);
+
+        let mut permutations_by_type: Vec<Vec<Vec<usize>>> = Vec::with_capacity(1 << 16);
+
+        for _i in 0..=u16::MAX {
+            permutations_by_type.push(Vec::new());
+        }
+
+        let mut placeholder: Vec<usize> = (0..set_length).collect();
+        let heap = Heap::new(&mut placeholder);
+        for permutation in heap {
+            for permutation_type in get_supported_permutation_types(&invert_permutation(&permutation)) {
+                permutations_by_type[permutation_type as usize].push(permutation.clone());
+            }
+        }
+
+        PermutationsCache {
+            permutations_by_type,
+            set_length,
+        }
+    }
+
+    pub fn get_permuted_vectors<T: Eq + Copy>(&self, ordered_vector_to_permute: &Vec<T>) -> Vec<Vec<T>> {
+        //println!("set_length: {}, vector: {:?}", self.set_length, ordered_vector_to_permute);
+        assert_eq!(ordered_vector_to_permute.len(), self.set_length);
+
+        let permutation_type = get_required_permutation_type(ordered_vector_to_permute);
+        let permutations = &self.permutations_by_type[permutation_type as usize];
+
+        return permutations.iter()
+            .map(|permutation| {
+                permutation.iter()
+                    .map(|&index| ordered_vector_to_permute[index])
+                    .collect()
+            })
+            .collect()
+    }
+}