package day19

import (
	"sort"
)

func merge(intervals [][]int) [][]int {
    const start, end = 0, 1

    var merged [][]int

    if len(intervals) > 1 {
        sort.Slice(intervals, func(i, j int) bool {
            return intervals[i][start] < intervals[j][start]
        })
    }

    for _, interval := range intervals {
        last := len(merged) - 1
        if last < 0 || interval[start] > merged[last][end] {
            merged = append(merged,
                []int{start: interval[start], end: interval[end]},
            )
        } else if interval[end] > merged[last][end] {
            merged[last][end] = interval[end]
        }
    }

    return merged[:len(merged):len(merged)]
}

func applyLessThan(intervals [][]int, n int) [][]int {
	var lessers [][]int
	for _, interval := range intervals {
		from := interval[0]
		if from >= n {
			continue
		}
		lessers = append(lessers, []int{from, n-1})
	}

	return lessers
}

func applyMoreThan(intervals [][]int, n int) [][]int {
	var greaters [][]int
	for _, interval := range intervals {
		to := interval[1]
		if to <= n {
			continue
		}
		greaters = append(greaters, []int{n+1, to})
	}
	// log.Printf(">>>> in applyMoreThan %d to %+v ; result %+v", n, intervals, greaters)

	return greaters
}