leetcode-go/leetcode/hard/391.perfect-rectangle.go

type pair struct {
	_1 int
	_2 int
}

func isRectangleCover(rectangles [][]int) bool {
	w, a, s, d := rectangles[0][3], rectangles[0][0], rectangles[0][1], rectangles[0][2]
	area := 0
	m := make(map[pair]bool)
	for i := range rectangles {
		cw, ca, cs, cd := rectangles[i][3], rectangles[i][0], rectangles[i][1], rectangles[i][2]
		w, a, s, d = maxInt(w, cw), minInt(a, ca), minInt(s, cs), maxInt(d, cd) // Record the max rectangle
		area += (cw - cs) * (cd - ca)
		put(&m, ca, cw) // If the coverage is perfect, all points appear in pair except tl, tr, bl and br.
		put(&m, cd, cw)
		put(&m, ca, cs)
		put(&m, cd, cs)
	}
	return m[pair{a, w}] && m[pair{d, w}] && m[pair{a, s}] && m[pair{d, s}] && len(m) == 4 && area == (w-s)*(d-a)
}

func put(m *map[pair]bool, x, y int) {
	p := pair{x, y}
	if _, ok := (*m)[p]; ok {
		delete(*m, p)
	} else {
		(*m)[p] = true
	}
}

func maxInt(x, y int) int {
	if x < y {
		return y
	}
	return x
}

func minInt(x, y int) int {
	if x < y {
		return x
	}
	return y
}