105 lines
2.4 KiB
Go
105 lines
2.4 KiB
Go
package witap
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import (
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"fmt"
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"strings"
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)
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type Resolver struct {
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Lines []string
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}
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type Position struct{ X, Y int }
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func (p *Position) Up() Position { return Position{X: p.X, Y: p.Y - 1} }
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func (p *Position) Down() Position { return Position{X: p.X, Y: p.Y + 1} }
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func (p *Position) Left() Position { return Position{X: p.X - 1, Y: p.Y} }
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func (p *Position) Right() Position { return Position{X: p.X + 1, Y: p.Y} }
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func NewResolverFromString(theMap string) Resolver {
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return Resolver{
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Lines: strings.Split(theMap, "\n"),
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}
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}
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func (r *Resolver) GetStartPosition() (Position, error) {
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for y, line := range r.Lines {
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if pos := strings.Index(line, "S"); pos != -1 {
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return Position{pos, y}, nil
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}
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}
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return Position{-1, -1}, fmt.Errorf("No such starting point")
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}
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func (r *Resolver) Run() (string, error) {
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startPos, err := r.GetStartPosition()
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if err != nil {
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return "", err
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}
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return r.Step(startPos, Position{-1, -1})
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}
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func (r *Resolver) PrintMap() {
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fmt.Println(strings.Join(r.Lines, "\n"))
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}
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func (p *Position) Continue(lastPos Position) Position {
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return Position{
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X: 2*p.X - lastPos.X,
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Y: 2*p.Y - lastPos.Y,
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}
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}
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func (r *Resolver) GetChar(position Position) string {
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return string(r.Lines[position.Y][position.X])
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}
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func (p *Position) AllDirections() []Position {
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return []Position{
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p.Up(), p.Down(), p.Left(), p.Right(),
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}
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}
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func (r *Resolver) Step(curPos, lastPos Position) (string, error) {
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if curPos.X < 0 || curPos.Y < 0 || curPos.Y >= len(r.Lines) || curPos.X >= len(r.Lines[curPos.Y]) {
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return "", fmt.Errorf("Invalid position")
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}
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letter := r.GetChar(curPos)
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if letter == "S" && lastPos.X != -1 {
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return "", fmt.Errorf("S must be the first position")
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} else if letter == "+" && lastPos.X == -1 {
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return "", fmt.Errorf("Cannot do this symbol after a start")
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}
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switch letter {
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case "S", "+":
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for _, nextPos := range curPos.AllDirections() {
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if nextPos == lastPos {
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continue
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}
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letter, err := r.Step(nextPos, curPos)
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if err == nil {
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return letter, err
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}
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}
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return "", fmt.Errorf("Nothing to do, cannot continue")
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case "-", "|":
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return r.Step(curPos.Continue(lastPos), curPos)
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case "V":
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return r.Step(curPos.Down(), curPos)
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case ">":
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return r.Step(curPos.Right(), curPos)
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case "<":
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return r.Step(curPos.Left(), curPos)
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case "^":
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return r.Step(curPos.Up(), curPos)
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case " ":
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return "", fmt.Errorf("Invalid path, cannot continue")
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default:
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return letter, nil
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}
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}
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