66 lines
1.3 KiB
Go
66 lines
1.3 KiB
Go
package year25
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import (
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"bufio"
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"fmt"
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"io"
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"log"
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"strings"
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)
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func Day3Part1(r io.Reader, l *log.Logger) (any, error) {
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return Day3(r, l, 2)
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}
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func Day3Part2(r io.Reader, l *log.Logger) (any, error) {
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return Day3(r, l, 12)
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}
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func Day3(r io.Reader, logger *log.Logger, size int) (int64, error) {
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scanner := bufio.NewScanner(r)
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scanner.Split(bufio.ScanLines)
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var sum int64
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findLargetDigit := func(digits []rune) (rune, int) {
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largestDigit := rune(0)
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index := 0
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for i := len(digits) - 1; i >= 0; i-- {
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if digits[i] >= largestDigit {
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largestDigit = digits[i]
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index = i
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}
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}
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return rune(largestDigit) - '0', index
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}
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for scanner.Scan() {
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text := strings.TrimSpace(scanner.Text())
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if text == "" {
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continue
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}
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line := []rune(text)
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parts := make([]byte, size)
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for index := range parts {
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digit, start := findLargetDigit(line[:len(line)+index-len(parts)+1])
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line = line[start+1:]
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if digit < 0 || digit > 9 {
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return 0, fmt.Errorf("ivalid char '%c' in line %s", digit, text)
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} else {
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parts[index] = byte(digit)
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}
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}
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logger.Println("line: ", text)
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var partSum int64
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for _, part := range parts {
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partSum *= 10
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partSum += int64(part)
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}
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logger.Println("got: ", partSum)
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logger.Println()
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sum += partSum
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}
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return sum, scanner.Err()
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}
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