add: leetcode 0391 solution

leetcode/0391.Perfect-Rectangle/391.Perfect Rectangle.go

@@ -0,0 +1,53 @@
+package leetcode
+
+type point struct {
+	x int
+	y int
+}
+
+func isRectangleCover(rectangles [][]int) bool {
+	minX, minY, maxA, maxB := rectangles[0][0], rectangles[0][1], rectangles[0][2], rectangles[0][3]
+	area := 0
+	cnt := make(map[point]int)
+	for _, v := range rectangles {
+		x, y, a, b := v[0], v[1], v[2], v[3]
+		area += (a - x) * (b - y)
+		minX = min(minX, x)
+		minY = min(minY, y)
+		maxA = max(maxA, a)
+		maxB = max(maxB, b)
+		cnt[point{x, y}]++
+		cnt[point{a, b}]++
+		cnt[point{x, b}]++
+		cnt[point{a, y}]++
+	}
+	if area != (maxA-minX)*(maxB-minY) ||
+		cnt[point{minX, minY}] != 1 || cnt[point{maxA, maxB}] != 1 ||
+		cnt[point{minX, maxB}] != 1 || cnt[point{maxA, minY}] != 1 {
+		return false
+	}
+	delete(cnt, point{minX, minY})
+	delete(cnt, point{maxA, maxB})
+	delete(cnt, point{minX, maxB})
+	delete(cnt, point{maxA, minY})
+	for _, v := range cnt {
+		if v != 2 && v != 4 {
+			return false
+		}
+	}
+	return true
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}