aoc2023/day-10/two.go

package main

import (
	"fmt"
	"math"

	log "github.com/sirupsen/logrus"
)

func debugPrint() {
	for _, points := range pointsArray {
		for _, point := range points.points {
			if contains(loop, point.coords) {
				fmt.Printf("%c ", point.identifier)
			} else {
				fmt.Printf(". ")
			}
		}
		fmt.Printf("\n")
	}
}

var loop []coords

// two returns the number of coords that sit inside the polygon
func two(lines []string) int {
	if log.GetLevel() == log.DebugLevel {
		debugPrint()
	}

	area := 0
	for i := 0; i < len(loop); i++ {
		next := loop[(i+1)%len(loop)]
		area += loop[i].X*next.Y - loop[i].Y*next.X
	}

	area = int(math.Abs(float64(area))) / 2

	return area - len(loop)/2 + 1
}