add day 07

y_2024/src/day_07.rs

@@ -0,0 +1,71 @@
+use crate::lib::parse_input;
+
+const INPUT_FILE: &str = "inputs/day_07.txt";
+const P1_OPERATIONS: [&str; 2] = ["*", "+"];
+const P2_OPERATIONS: [&str; 3] = ["*", "+", "||"];
+
+/// Parses the input file into a list of targets and their associated values.
+fn get_target_and_values() -> Vec<(i64, Vec<i64>)> {
+    parse_input(INPUT_FILE)
+        .iter()
+        .map(|line| {
+            let parts = line.split_whitespace().collect::<Vec<&str>>();
+            let target = parts[0].replace(':', "").parse::<i64>().unwrap();
+            let values = parts[1..]
+                .iter()
+                .map(|num| num.parse::<i64>().unwrap())
+                .collect();
+            (target, values)
+        })
+        .collect()
+}
+
+/// Evaluates a sequence of operations on a list of values from left to right.
+fn evaluate(values: &[i64], operations: &[&str]) -> i64 {
+    let mut result = values[0];
+    for (i, operation) in operations.iter().enumerate() {
+        match *operation {
+            "*" => result *= values[i + 1],
+            "+" => result += values[i + 1],
+            "||" => {
+                let concatenated = format!("{}{}", result, values[i + 1])
+                    .parse::<i64>()
+                    .expect("Concatenation failed");
+                result = concatenated;
+            }
+            _ => panic!("Invalid operation"),
+        }
+    }
+    result
+}
+
+/// Solves the problem using the specified set of operations.
+fn solve(operations: &[&str]) -> i64 {
+    let target_and_values = get_target_and_values();
+    let mut sum = 0;
+
+    for (target, values) in target_and_values {
+        let num_operations = values.len() - 1;
+        let all_combinations = (0..operations.len().pow(num_operations as u32)).map(|n| {
+            (0..num_operations)
+                .map(|i| operations[(n / operations.len().pow(i as u32)) % operations.len()])
+                .collect::<Vec<_>>()
+        });
+
+        for ops in all_combinations {
+            if evaluate(&values, &ops) == target {
+                sum += target;
+                break;
+            }
+        }
+    }
+    sum
+}
+
+pub fn part_1() -> i64 {
+    solve(&P1_OPERATIONS)
+}
+
+pub fn part_2() -> i64 {
+    solve(&P2_OPERATIONS)
+}

y_2024/src/main.rs

@@ -9,6 +9,7 @@ mod day_03;
 mod day_04;
 mod day_05;
 mod day_06;
+mod day_07;
 mod lib;
 
 fn main() {
@@ -17,5 +18,6 @@ fn main() {
     // println!("day 3: p1 {} | p2 {}", day_03::part_1(), day_03::part_2());
     // println!("day 4: p1 {} | p2 {}", day_04::part_1(), day_04::part_2());
     // println!("day 5: p1 {} | p2 {}", day_05::part_1(), 0);
-    println!("day 5: p1 {} | p2 {}", day_06::part_1(), day_06::part_2());
+    // println!("day 6: p1 {} | p2 {}", day_06::part_1(), day_06::part_2());
+    println!("day 7: p1 {} | p2 {}", day_07::part_1(), day_07::part_2());
 }