110 lines
2.2 KiB
Go
110 lines
2.2 KiB
Go
package one
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import (
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"bufio"
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"fmt"
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"os"
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"strconv"
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)
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type expenseReport struct {
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expenses []int
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}
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func (e *expenseReport) load(filename string) error {
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file, err := os.Open(filename)
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if err != nil {
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return err
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}
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defer file.Close()
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scanner := bufio.NewScanner(file)
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for scanner.Scan() {
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value, err := strconv.Atoi(scanner.Text())
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if err != nil {
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return err
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}
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e.expenses = append(e.expenses, value)
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}
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return nil
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}
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func (e *expenseReport) findPairAndMultiply(target int) (int, error) {
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for i := 0; i < len(e.expenses); i++ {
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if e.expenses[i] > target {
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continue
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}
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for j := i + 1; j < len(e.expenses); j++ {
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if e.expenses[j] > target {
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continue
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}
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if (e.expenses[i] + e.expenses[j]) == target {
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return e.expenses[i] * e.expenses[j], nil
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}
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}
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}
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return -1, fmt.Errorf("Unable to find target pair that sums to %d", target)
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}
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func (e *expenseReport) findTrioAndMultiply(target int) (int, error) {
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for i := 0; i < len(e.expenses); i++ {
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if e.expenses[i] > target {
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continue
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}
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for j := i + 1; j < len(e.expenses); j++ {
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if e.expenses[j] > target {
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continue
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}
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for k := j + 1; k < len(e.expenses); k++ {
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if e.expenses[k] > target {
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continue
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}
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if (e.expenses[i] + e.expenses[j] + e.expenses[k]) == target {
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return e.expenses[i] * e.expenses[j] * e.expenses[k], nil
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}
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}
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}
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}
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return -1, fmt.Errorf("Unable to find target pair that sums to %d", target)
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}
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// PartOne Find the multiplied value of the two expenses totalling 2020
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func PartOne() string {
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report := expenseReport{}
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err := report.load("one/expenses.txt")
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if err != nil {
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return fmt.Sprintf("Unable to load expenses: %s", err.Error())
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}
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result, err := report.findPairAndMultiply(2020)
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if err != nil {
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return err.Error()
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}
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return fmt.Sprintf("The output of the expenses summing to 2020 is %d", result)
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}
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func PartTwo() string {
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report := expenseReport{}
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err := report.load("one/expenses.txt")
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if err != nil {
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return fmt.Sprintf("Unable to load expenses: %s", err.Error())
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}
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result, err := report.findTrioAndMultiply(2020)
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if err != nil {
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return err.Error()
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}
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return fmt.Sprintf("The output of the expenses summing to 2020 is %d", result)
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}
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