feat: solve day 3 part 1

README.md

@@ -28,7 +28,7 @@ go test ./cmd/01
 |-----|-------------------------------------------------|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | 01  | [Problem](https://adventofcode.com/2025/day/1)  | [Solution](./cmd/01/) | Part 1 seemed straight forward enough. Part 2 completely stumped me. The trickiest part was not counting zero's twice when you ended and then started from there.                      |
 | 02  | [Problem](https://adventofcode.com/2025/day/2)  | [Solution](./cmd/02/) | Part 1 should have been super straight-forward, but some whitespace screwed up my parsing of the final range. I some how was able to stumble over a solution to part 2 rather blindly. |
-| 03  | [Problem](https://adventofcode.com/2025/day/3)  | [Solution](./cmd/03/) |                                                                                                                                                                                        |
+| 03  | [Problem](https://adventofcode.com/2025/day/3)  | [Solution](./cmd/03/) | Part 1 intuitively makes you think you only care about highest nums, but then you need to consider placement.                                                                          |
 | 04  | [Problem](https://adventofcode.com/2025/day/4)  | [Solution](./cmd/04/) |                                                                                                                                                                                        |
 | 05  | [Problem](https://adventofcode.com/2025/day/5)  | [Solution](./cmd/05/) |                                                                                                                                                                                        |
 | 06  | [Problem](https://adventofcode.com/2025/day/6)  | [Solution](./cmd/06/) |                                                                                                                                                                                        |

cmd/03/bank/bank.go

@@ -0,0 +1,102 @@
+// Package bank represents a bank of batteries
+package bank
+
+import (
+	"fmt"
+	"strconv"
+)
+
+type Bank interface {
+	Joltage() int
+	Cells() []int
+}
+
+type bank struct {
+	cells []int
+}
+
+func From(line string) Bank {
+	cells := []int{}
+
+	for _, char := range line {
+		num, _ := strconv.Atoi(string(char))
+		cells = append(cells, num)
+	}
+
+	return bank{
+		cells: cells,
+	}
+}
+
+type cell struct {
+	index int
+	value int
+}
+
+func (b bank) Joltage() int {
+	// TODO: We still need to
+	// find the max
+	// however we should then
+	// find the next max to the
+	// left of the highest
+	// and find the next max to
+	// the right of the higest
+	// we should then see what
+	// the large number we can make
+	// with these values
+
+	max := cell{
+		value: -1,
+	}
+
+	for ci, cv := range b.cells {
+		if cv > max.value {
+			max = cell{
+				index: ci,
+				value: cv,
+			}
+		}
+	}
+
+	maxLeft := cell{
+		value: -1,
+	}
+
+	for ci, cv := range b.cells[:max.index] {
+		if cv > maxLeft.value {
+			maxLeft = cell{
+				index: ci,
+				value: cv,
+			}
+		}
+	}
+
+	maxRight := cell{
+		value: -1,
+	}
+
+	for ci, cv := range b.cells[max.index+1:] {
+		if cv > maxRight.value {
+			maxRight = cell{
+				index: ci,
+				value: cv,
+			}
+		}
+	}
+
+	maxInTensPlace := fmt.Sprintf("%d%d", max.value, maxRight.value)
+	maxInOnesPlace := fmt.Sprintf("%d%d", maxLeft.value, max.value)
+
+	maxInTensPlaceAsNumber, _ := strconv.Atoi(maxInTensPlace)
+	maxInOnesPlaceAsNumber, _ := strconv.Atoi(maxInOnesPlace)
+
+	if maxInTensPlaceAsNumber > maxInOnesPlaceAsNumber {
+		return maxInTensPlaceAsNumber
+	}
+
+	return maxInOnesPlaceAsNumber
+}
+
+func (b bank) Cells() []int {
+	return b.cells
+}

cmd/03/bank/bank_test.go

@@ -0,0 +1,53 @@
+package bank_test
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/StevanFreeborn/advent-of-code-2025/cmd/03/bank"
+)
+
+func TestFrom(t *testing.T) {
+	expected := []int{1, 2, 3, 4, 5}
+	input := "12345"
+
+	result := bank.From(input)
+
+	if slices.Equal(result.Cells(), expected) == false {
+		t.Errorf("got %v but wanted %v", result.Cells(), expected)
+	}
+}
+
+type testCase struct {
+	bank     bank.Bank
+	expected int
+}
+
+func TestJoltage(t *testing.T) {
+	testCases := []testCase{
+		{
+			bank:     bank.From("987654321111111"),
+			expected: 98,
+		},
+		{
+			bank:     bank.From("811111111111119"),
+			expected: 89,
+		},
+		{
+			bank:     bank.From("234234234234278"),
+			expected: 78,
+		},
+		{
+			bank:     bank.From("818181911112111"),
+			expected: 92,
+		},
+	}
+
+	for _, testCase := range testCases {
+		result := testCase.bank.Joltage()
+
+		if result != testCase.expected {
+			t.Errorf("got %d but wanted %d", result, testCase.expected)
+		}
+	}
+}

cmd/03/main.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"github.com/StevanFreeborn/advent-of-code-2025/cmd/03/bank"
+	"github.com/StevanFreeborn/advent-of-code-2025/internal/file"
+)
+
+func SolvePartOne(filePath string) int {
+	input := file.ReadLines(filePath)
+	total := 0
+
+	for _, line := range input {
+		bank := bank.From(line)
+		total += bank.Joltage()
+	}
+
+	return total
+}

cmd/03/main_test.go

@@ -0,0 +1,27 @@
+package main_test
+
+import (
+	"testing"
+
+	solution "github.com/StevanFreeborn/advent-of-code-2025/cmd/03"
+)
+
+func TestSolvePartOneWithExampleInput(t *testing.T) {
+	expected := 357
+
+	result := solution.SolvePartOne("EXAMPLE.txt")
+
+	if result != expected {
+		t.Errorf("got %d but wanted %d", result, expected)
+	}
+}
+
+func TestSolvePartOneWithInput(t *testing.T) {
+	expected := 17113
+
+	result := solution.SolvePartOne("INPUT.txt")
+
+	if result != expected {
+		t.Errorf("got %d but wanted %d", result, expected)
+	}
+}

internal/file/file.go

@@ -6,6 +6,9 @@ import (
 	"os"
 )
 
+// TODO: Implement a StreamLines method
+// in the file package
+
 func ReadLines(filePath string) []string {
 	lines := []string{}