Implement 2025 day 3 in bash

2025/day03/solve.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+
+if [[ $# -lt 1 ]]; then
+    echo "Usage: $0 <input file>" >&2
+    exit 1
+fi
+
+joltage() {
+    local first second c i
+
+    first=0
+    second=0
+
+    for ((i = 0; i < ${#1}; i++)); do
+        c="${1:$i:1}"
+
+        if [[ $second -gt $first ]]; then
+            first="$second"
+            second="$c"
+        elif [[ $c -gt $second ]]; then
+            second="$c"
+        fi
+    done
+
+    echo "$first$second"
+}
+
+joltage2() {
+    local c i d e n digits
+
+    digits=(0 0 0 0 0 0 0 0 0 0 0 0)
+
+    for ((i = 0; i < ${#1}; i++)); do
+        c="${1:$i:1}"
+
+        for ((d = 0; d < 11; d++)); do
+            if [[ ${digits[((d + 1))]} -gt ${digits[$d]} ]]; then
+                for ((e = d; e < 11; e++)); do
+                    n=$((e + 1))
+                    digits[e]=${digits[n]}
+                done
+                digits[11]="0"
+                break
+            fi
+        done
+
+        if [[ $c -gt ${digits[11]} ]]; then
+            digits[11]="$c"
+        fi
+    done
+
+    printf "%s" "${digits[@]}"
+}
+
+total=0
+total2=0
+
+while IFS="" read -r line || [[ -n "$p" ]]; do
+    ((total += $(joltage "$line")))
+    ((total2 += $(joltage2 "$line")))
+done <"$1"
+
+echo "$total"
+echo "$total2"