题目：

题解：

func isRectangleCover(rectangles [][]int) bool {type point struct{ x, y int }area, minX, minY, maxX, maxY := 0, rectangles[0][0], rectangles[0][1], rectangles[0][2], rectangles[0][3]cnt := map[point]int{}for _, rect := range rectangles {x, y, a, b := rect[0], rect[1], rect[2], rect[3]area += (a - x) * (b - y)minX = min(minX, x)minY = min(minY, y)maxX = max(maxX, a)maxY = max(maxY, b)cnt[point{x, y}]++cnt[point{x, b}]++cnt[point{a, y}]++cnt[point{a, b}]++}if area != (maxX-minX)*(maxY-minY) || cnt[point{minX, minY}] != 1 || cnt[point{minX, maxY}] != 1 || cnt[point{maxX, minY}] != 1 || cnt[point{maxX, maxY}] != 1 {return false}delete(cnt, point{minX, minY})delete(cnt, point{minX, maxY})delete(cnt, point{maxX, minY})delete(cnt, point{maxX, maxY})for _, c := range cnt {if c != 2 && c != 4 {return false}}return true
}func min(a, b int) int {if a > b {return b}return a
}func max(a, b int) int {if b > a {return b}return a
}