day2

exercises/2025/03-lobby/README.md

@@ -0,0 +1,29 @@
+# [Day 3: Lobby](https://adventofcode.com/2025/day/3)
+
+<!-- These are helper text to make formatting the yearly readme consistent and easier...
+
+[Day 3: Lobby][rm3]
+[Go][go3]
+[Python][py3]
+
+[rm3]: 03-lobby/README.md
+[go3]: 03-lobby/go
+[py3]: 03-lobby/py
+
+-->
+
+## Go
+
+```text
+< section intentionally left blank >
+```
+
+## Python
+
+```text
+< section intentionally left blank >
+```
+
+## 2025 Run Times
+
+![2025 exercise run-time graphs](../run-times.png)

exercises/2025/03-lobby/go/exercise.go

@@ -0,0 +1,97 @@
+package exercises
+
+import (
+	"strings"
+
+	"github.com/asphaltbuffet/advent-of-code/internal/common"
+)
+
+// Exercise for Advent of Code 2025 day 3.
+type Exercise struct {
+	common.BaseExercise
+}
+
+// One returns the answer to the first part of the exercise.
+func (e Exercise) One(instr string) (any, error) {
+	var sum int
+	for bank := range strings.Lines(instr) {
+		sum += Largest(strings.Trim(bank, "\n"))
+		// sum += LongLargest(strings.Trim(bank, "\n"), 2)
+	}
+
+	return sum, nil
+}
+
+// Two returns the answer to the second part of the exercise.
+func (e Exercise) Two(instr string) (any, error) {
+	var sum int
+	for bank := range strings.Lines(instr) {
+		sum += LongLargest(strings.Trim(bank, "\n"), 12)
+	}
+
+	return sum, nil
+}
+
+// Largest creates the max 2-digit integer from consecutive integers in a string.
+// It assumes that every character in the string is '0' -> '9'.
+func Largest(b string) int {
+	var l int
+	var r int
+
+	for i := 0; i < len(b)-1; i++ {
+		n := int(b[i] - '0')
+		if n > l {
+			l = n
+			r = -1
+		} else if n > r {
+			r = n
+		}
+	}
+
+	//set r to last value if unset
+	n := int(b[len(b)-1] - '0')
+	if r < n {
+		r = n
+	}
+
+	return l*10 + r
+}
+
+func LongLargest(b string, digits int) int {
+	bank := make([]int, len(b))
+
+	for i, r := range b {
+		bank[i] = int(r - '0')
+	}
+	// fmt.Println("bank: ", bank)
+
+	out := 0
+	remaining := digits
+
+	for i := 0; remaining > 0; {
+		window := len(b) - i - remaining + 1
+		// fmt.Printf("i=%d w=%d r= %d out=%d\n", i, window, remaining, out)
+
+		m, idx := MaxInRange(bank[i : i+window])
+		out = out*10 + m
+
+		i += idx + 1
+		remaining--
+	}
+
+	return out
+}
+
+func MaxInRange(b []int) (int, int) {
+	idx := 0
+	m := 0
+
+	for i, n := range b {
+		if n > m {
+			m = n
+			idx = i
+		}
+	}
+
+	return m, idx
+}

exercises/2025/03-lobby/info.json

@@ -0,0 +1,60 @@
+{
+  "id": "2025-03",
+  "title": "Lobby",
+  "year": 2025,
+  "day": 3,
+  "url": "https://adventofcode.com/2025/day/3",
+  "data": {
+    "inputFile": "input.txt",
+    "testCases": {
+      "one": [
+        {
+          "input": "987654321111111",
+          "expected": "98"
+        },
+        {
+          "input": "811111111111119",
+          "expected": "89"
+        },
+        {
+          "input": "234234234234278",
+          "expected": "78"
+        },
+        {
+          "input": "818181911112111",
+          "expected": "92"
+        },
+        {
+          "input": "987654321111111\n811111111111119\n234234234234278\n818181911112111",
+          "expected": "357"
+        }
+      ],
+      "two": [
+        {
+          "input": "987654321111111",
+          "expected": "987654321111"
+        },
+        {
+          "input": "811111111111119",
+          "expected": "811111111119"
+        },
+        {
+          "input": "234234234234278",
+          "expected": "434234234278"
+        },
+        {
+          "input": "818181911112111",
+          "expected": "888911112111"
+        },
+        {
+          "input": "987654321111111\n811111111111119\n234234234234278\n818181911112111",
+          "expected": "3121910778619"
+        }
+      ]
+    },
+    "answers": {
+      "a": "17087",
+      "b": ""
+    }
+  }
+}

exercises/2025/README.md

@@ -8,7 +8,7 @@
 | -------------------------------- | :---: | --------- |
 | [Day 1: Secret Entrance][rm1]    |  ⭐⭐ | [][go1]  |
 | [Day 2: Gift Shop][rm2]          |  ⭐⭐ | [][go2]  |
-| Day 3                            |  ☆☆   |           |
+| [Day 3: Lobby][rm3]              |  ☆☆   | [Go][go3] |
 | Day 4                            |  ☆☆   |           |
 | Day 5                            |  ☆☆   |           |
 | Day 6                            |  ☆☆   |           |
@@ -49,3 +49,5 @@ Day   -Part 1-   -Part 2-
 [go1]: 01-secretEntrance/go
 [rm2]: 02-giftShop/README.md
 [go2]: 02-giftShop/go
+[rm3]: 03-lobby/README.md
+[go3]: 03-lobby/go

go.mod

@@ -1,6 +1,6 @@
 module github.com/asphaltbuffet/advent-of-code
 
-go 1.23
+go 1.25.4
 
 require github.com/stretchr/testify v1.10.0