day 11

day11/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day11"
+version = "0.1.0"

day11/Cargo.toml

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+[package]
+name = "day11"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day11/input.txt

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day11/src/main.rs

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+use std::fs::read_to_string;
+use std::iter::zip;
+use std::time::Instant;
+
+fn naive_implementation(input_str: &str) -> (i64, i64) {
+    let width = input_str.lines().next().unwrap().len();
+    let height = input_str.lines().count();
+    // These arrays will hold mapping of initial coordinates to coordinates after expansion
+    // In the initial loop the elements will be 1 for empty and 0 for non-empty
+    let mut x_mapping: Vec<i64> = vec![1; width];
+    let mut y_mapping: Vec<i64> = vec![1; height];
+    // List of tuples of galaxy coordinates
+    let mut galaxies: Vec::<(i64, i64)> = vec![];
+    for (j, line) in input_str.lines().enumerate() {
+        for (i, c) in line.bytes().enumerate() {
+            if c == b'#' {
+                x_mapping[i] = 0;
+                y_mapping[j] = 0;
+                galaxies.push((i as i64, j as i64));
+            }
+        }
+    }
+    // Convert mappings of 0 and 1 to accumulated coordinate mappings
+    // mapping1 is for task 1, mapping2 is for task 2, mapping2 is a purely output argument
+    let accumulate_mappings =
+        |mapping1: &mut Vec<i64>, mapping2: &mut Vec<i64>| {
+            let mut accmulator: i64 = 0;
+            let mut accmulator2: i64 = 0;
+            for (x1, x2) in zip(mapping1.iter_mut(), mapping2.iter_mut()) {
+                accmulator += *x1;
+                accmulator2 += *x1 * 999999;
+                *x1 = accmulator;
+                *x2 = accmulator2;
+                accmulator += 1;
+                accmulator2 += 1;
+            }
+        };
+    // Convert galaxy coordinates using mapping arrays
+    // Returns a copy becuase we need two different mappings for two tasks
+    let map_galaxies =
+        |galaxies: &Vec<(i64, i64)>, x_mapping: &Vec<i64>, y_mapping: &Vec<i64>| {
+            galaxies.iter().map(|&(x, y)| (x_mapping[x as usize], y_mapping[y as usize])).collect::<Vec<_>>()
+        };
+    // Calculating the distances pairwise
+    let sum_distances =
+        |galaxies: &Vec<(i64, i64)>| {
+            let mut sum1 = 0;
+            for (i, &(x1, y1)) in galaxies.iter().enumerate() {
+                for &(x2, y2) in galaxies[i + 1..].iter() {
+                    sum1 += (x2 - x1).abs() + (y2 - y1).abs();
+                }
+            }
+            sum1
+        };
+    let mut x_mapping2: Vec<i64> = vec![0; width];
+    let mut y_mapping2: Vec<i64> = vec![0; height];
+    accumulate_mappings(&mut x_mapping, &mut x_mapping2);
+    accumulate_mappings(&mut y_mapping, &mut y_mapping2);
+    let galaxies_mapped1 = map_galaxies(&galaxies, &x_mapping, &y_mapping);
+    let galaxies_mapped2 = map_galaxies(&galaxies, &x_mapping2, &y_mapping2);
+    let sum1 = sum_distances(&galaxies_mapped1);
+    let sum2 = sum_distances(&galaxies_mapped2);
+    (sum1, sum2)
+}
+
+fn improved_implementation(input_str: &str) -> (i64, i64) {
+    let width = input_str.lines().next().unwrap().len();
+    let height = input_str.lines().count();
+    // These arrays will hold mapping of initial coordinates to coordinates after expansion
+    // In the initial loop the elements will be 1 for empty and 0 for non-empty
+    let mut x_mapping: Vec<i64> = vec![1; width];
+    let mut y_mapping: Vec<i64> = vec![1; height];
+    // These arrays hold a tupe of row/col index and count of galaxies in that index
+    // They will be later mapped using mapping arrays
+    let mut x_counters = (0..width)
+        .map(|i| (i as i64, 0i64)).collect::<Vec<_>>();
+    let mut y_counters = (0..height)
+        .map(|i| (i as i64, 0i64)).collect::<Vec<_>>();
+    for (j, line) in input_str.lines().enumerate() {
+        for (i, c) in line.bytes().enumerate() {
+            if c == b'#' {
+                x_mapping[i] = 0;
+                y_mapping[j] = 0;
+                let (_, count_x) = &mut x_counters[i];
+                *count_x += 1;
+                let (_, count_y) = &mut y_counters[j];
+                *count_y += 1;
+            }
+        }
+    }
+    // Remove empty rows/cols
+    x_counters.retain(|(_, counter)| *counter > 0);
+    y_counters.retain(|(_, counter)| *counter > 0);
+    // Convert mappings of 0 and 1 to accumulated coordinate mappings
+    // mapping1 is for task 1, mapping2 is for task 2, mapping2 is a purely output argument
+    let accumulate_mappings =
+        |mapping1: &mut Vec<i64>, mapping2: &mut Vec<i64>| {
+            let mut accmulator: i64 = 0;
+            let mut accmulator2: i64 = 0;
+            for (x1, x2) in zip(mapping1.iter_mut(), mapping2.iter_mut()) {
+                accmulator += *x1;
+                accmulator2 += *x1 * 999999;
+                *x1 = accmulator;
+                *x2 = accmulator2;
+                accmulator += 1;
+                accmulator2 += 1;
+            }
+        };
+    // Convert counter indices using mapping arrays
+    // Returns a copy becuase we need two different mappings for two tasks
+    let map_counter_coordinates =
+        |counters: &Vec<(i64, i64)>, mapping: &Vec<i64>| {
+            counters.iter().map(|&(i, counter)| (mapping[i as usize], counter)).collect::<Vec<_>>()
+        };
+    // Sum all distances along one dimension
+    let sum_distances =
+        |counters: &Vec<(i64, i64)>| {
+            let mut sum1 = 0;
+            for (i, &(pos1, counter1)) in counters.iter().enumerate() {
+                for &(pos2, counter2) in counters[i + 1..].iter() {
+                    sum1 += (pos2 - pos1) * counter1 * counter2;
+                }
+            }
+            sum1
+        };
+    let mut x_mapping2: Vec<i64> = vec![0; width];
+    let mut y_mapping2: Vec<i64> = vec![0; height];
+    accumulate_mappings(&mut x_mapping, &mut x_mapping2);
+    accumulate_mappings(&mut y_mapping, &mut y_mapping2);
+    let x_counters1 = map_counter_coordinates(&x_counters, &x_mapping);
+    let y_counters1 = map_counter_coordinates(&y_counters, &y_mapping);
+    let x_counters2 = map_counter_coordinates(&x_counters, &x_mapping2);
+    let y_counters2 = map_counter_coordinates(&y_counters, &y_mapping2);
+    let sum1 = sum_distances(&x_counters1) + sum_distances(&y_counters1);
+    let sum2 = sum_distances(&x_counters2) + sum_distances(&y_counters2);
+    (sum1, sum2)
+}
+
+fn main() {
+    let time_start = Instant::now();
+    let input_str = read_to_string("input.txt").unwrap();
+    let time_start_no_io = Instant::now();
+    // Option to
+    let mut sum1 = 0i64;
+    let mut sum2 = 0i64;
+    // Solve multiple times for performance testing
+    for _ in 0..1000 {
+        //(sum1, sum2) = naive_implementation(&input_str);
+        (sum1, sum2) = improved_implementation(&input_str);
+    }
+    let elapsed = time_start.elapsed().as_micros();
+    let elapsed_no_io = time_start_no_io.elapsed().as_micros();
+    println!("Time: {}us", elapsed);
+    println!("Time without file i/o: {}us", elapsed_no_io);
+    println!("Sum1: {}", sum1);
+    println!("Sum1: {}", sum2);
+}