feat: solve day 7

Author: Flashky

README.md

@@ -9,7 +9,7 @@
 - [Day 4 - Ceres Search](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day04)
 - [Day 5 - Print Queue](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day05)
 - [Day 6 - Guard Gallivant](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day06)
-- [Day 7](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day07)
+- [Day 7 - Bridge Repair](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day07)
 - [Day 8](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day08)
 - [Day 9](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day09)
 - [Day 10](https://github.com/Flashky/advent-of-code-2024/tree/master/src/main/java/com/adventofcode/flashk/day10)

src/main/java/com/adventofcode/flashk/day07/BridgeRepair.java

@@ -0,0 +1,17 @@
+package com.adventofcode.flashk.day07;
+
+import java.util.List;
+
+public class BridgeRepair {
+
+    private final List<Equation> equations;
+
+    public BridgeRepair(List<String> inputs) {
+        equations = inputs.stream().map(Equation::new).toList();
+    }
+
+    public long solve(boolean concatenate) {
+        return equations.stream().mapToLong(eq -> eq.solve(concatenate)).sum();
+    }
+
+}

src/main/java/com/adventofcode/flashk/day07/Equation.java

@@ -0,0 +1,60 @@
+package com.adventofcode.flashk.day07;
+
+import lombok.Getter;
+
+import java.util.Arrays;
+import java.util.Deque;
+import java.util.ArrayDeque;
+import java.util.stream.Collectors;
+
+public class Equation {
+
+    private final long result;
+    private final Deque<Integer> operators;
+    private boolean concatenate;
+
+    public Equation(String input) {
+        String[] inputParts = input.split(":");
+        result = Long.parseLong(inputParts[0]);
+        operators = Arrays.stream(inputParts[1].split(" "))
+                .skip(1).map(Integer::parseInt).collect(Collectors.toCollection(ArrayDeque::new));
+    }
+
+    public long solve(boolean concatenate) {
+        this.concatenate = concatenate;
+        return hasSolution(operators, 0) ? result : 0;
+    }
+
+    private boolean hasSolution(Deque<Integer> operators, long partialResult) {
+
+        if(operators.isEmpty()) {
+            return partialResult == result;
+        }
+
+        Integer currentOperator = operators.poll();
+        boolean hasSolution = hasSolution(operators, partialResult + currentOperator);
+
+        if(!hasSolution && partialResult != 0) {
+            hasSolution = hasSolution(operators, partialResult * currentOperator);
+        } else if(partialResult == 0) {
+            hasSolution = hasSolution(operators, currentOperator);
+        }
+
+        if(!hasSolution && concatenate) {
+            StringBuilder sb = new StringBuilder();
+
+            if(partialResult != 0) {
+                sb.append(partialResult);
+            }
+
+            long concatenatedPartialResult = Long.parseLong(sb.append(currentOperator).toString());
+            hasSolution = hasSolution(operators, concatenatedPartialResult);
+
+        }
+
+        operators.addFirst(currentOperator);
+
+        return hasSolution;
+    }
+}
+

src/main/java/com/adventofcode/flashk/day07/README.md

@@ -1,3 +1,3 @@
-# Day 7: 
+# Day 7: Bridge Repair
 
 [https://adventofcode.com/2024/day/7](https://adventofcode.com/2024/day/7)

src/test/java/com/adventofcode/flashk/day07/Day07Test.java

@@ -3,7 +3,6 @@
 import java.util.List;
 
 import org.junit.jupiter.api.BeforeAll;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.MethodOrderer.OrderAnnotation;
 import org.junit.jupiter.api.Order;
@@ -19,9 +18,10 @@
 import com.adventofcode.flashk.common.test.utils.Timer;
 import com.adventofcode.flashk.common.test.utils.Input;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 @DisplayName(TestDisplayName.DAY_07)
 @TestMethodOrder(OrderAnnotation.class)
-@Disabled // TODO Remove comment when implemented
 public class Day07Test extends PuzzleTest {
 
 	private final static String INPUT_FOLDER = TestFolder.DAY_07;
@@ -43,6 +43,9 @@ public void testSolvePart1Sample() {
 
 		// Read input file
 		List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE_SAMPLE);
+
+		BridgeRepair bridgeRepair = new BridgeRepair(inputs);
+		assertEquals(3749, bridgeRepair.solve(false));
 
 	}
 
@@ -57,7 +60,9 @@ public void testSolvePart1Input() {
 
 		// Read input file
 		List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE);
-		
+		BridgeRepair bridgeRepair = new BridgeRepair(inputs);
+
+		assertEquals(3351424677624L, bridgeRepair.solve(false));
 	}
 
 	@Test
@@ -71,7 +76,10 @@ public void testSolvePart2Sample() {
 
 		// Read input file
 		List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE_SAMPLE);
-		
+		BridgeRepair bridgeRepair = new BridgeRepair(inputs);
+
+		assertEquals(11387, bridgeRepair.solve(true));
+
 	}
 
 	@Test
@@ -85,7 +93,9 @@ public void testSolvePart2Input() {
 
 		// Read input file
 		List<String> inputs = Input.readStringLines(INPUT_FOLDER, TestFilename.INPUT_FILE);
-		
+		BridgeRepair bridgeRepair = new BridgeRepair(inputs);
+
+		assertEquals(204976636995111L, bridgeRepair.solve(true));
 	}
 
 }