day 7: part 2: rust

2024/days/07/part2/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "part1"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

2024/days/07/part2/src/main.rs

@@ -0,0 +1,53 @@
+
+fn concatenate_integers(a: u64, b: u64) -> u64 {
+  let a_str = a.to_string();
+  let b_str = b.to_string();
+  let result_str = a_str + &b_str;
+  let result: u64 = result_str.parse().unwrap();
+  return result;
+}
+
+fn can_be_evaluated_to_aux(operands: &Vec<u64>, target: u64, current: u64, index: usize) -> bool {
+  if index == 0 {
+    return can_be_evaluated_to_aux(operands, target, operands[0], index + 1);
+  } else if index == operands.len() {
+    if current == target {
+      return true;
+    } else {
+      return false;
+    }
+  } else {
+    return
+      can_be_evaluated_to_aux(operands, target, current * operands[index], index + 1)
+        || can_be_evaluated_to_aux(operands, target, current + operands[index], index + 1)
+        || can_be_evaluated_to_aux(operands, target, concatenate_integers(current, operands[index]), index + 1)
+    ;
+  }
+}
+
+fn can_be_evaluated_to(operands: &Vec<u64>, target: u64) -> bool {
+  return can_be_evaluated_to_aux(operands, target, 0, 0);
+}
+
+fn main() -> std::io::Result<()> {
+    let mut total: u64 = 0;
+    for line in std::io::stdin().lines() {
+        let line = line.unwrap();
+      if line != "".to_string() {
+        let mut parts = line.split(":");
+        let target = parts.next().unwrap();
+        let target = target.parse::<u64>().unwrap();
+        let operands: Vec<u64> = parts.next()
+                                      .unwrap()
+                                      .split(" ")
+                                      .skip(1)
+                                      .map(|e| e.parse::<u64>().unwrap())
+                                      .collect();
+        if can_be_evaluated_to(&operands, target) {
+          total += target;
+        }
+      }
+    }
+    println!("{}", total);
+    Ok(())
+}