850 solved

Author: aQua

Algorithms/0850.rectangle-area-ii/rectangle-area-ii.go

@@ -1,15 +1,82 @@
 package problem0850
 
+import (
+	"sort"
+)
+
 const mod = 1e9 + 7
 
 func rectangleArea(rectangles [][]int) int {
-	sum := 0
+	xs := getXs(rectangles)
+	sort.Ints(xs)
+
+	idxX := make(map[int]int, 2*len(xs))
+	for k, x := range xs {
+		idxX[x] = k
+	}
+
+	count := make([]int, len(xs))
+
+	L := make([][]int, 0, 2*len(rectangles))
+
 	for _, r := range rectangles {
-		sum += area(r)
+		x1, y1, x2, y2 := r[0], r[1], r[2], r[3]
+		L = append(L,
+			[]int{y1, x1, x2, 1},
+			[]int{y2, x1, x2, -1},
+		)
 	}
-	return sum % mod
+
+	sort.Slice(L, func(i int, j int) bool {
+		eq0 := L[i][0] == L[j][0]
+		eq1 := L[i][1] == L[j][1]
+		eq2 := L[i][2] == L[j][2]
+		if eq0 && eq1 && eq2 {
+			return L[i][3] < L[j][3]
+		}
+		if eq0 && eq1 {
+			return L[i][2] < L[j][2]
+		}
+		if eq0 {
+			return L[i][1] < L[j][1]
+		}
+		return L[i][0] < L[j][0]
+	})
+
+	curY, curXSum, area := 0, 0, 0
+
+	for _, l := range L {
+		y, x1, x2, sig := l[0], l[1], l[2], l[3]
+		area += (y - curY) * curXSum
+		curY = y
+		for i := idxX[x1]; i < idxX[x2]; i++ {
+			count[i] += sig
+		}
+		curXSum = 0
+		for i := 0; i+1 < len(count); i++ {
+			if count[i] != 0 {
+				curXSum += xs[i+1] - xs[i]
+			}
+		}
+
+	}
+
+	return area % mod
 }
 
-func area(r []int) int {
-	return ((r[2] - r[0]) * (r[3] - r[1])) % mod
+func getXs(rects [][]int) []int {
+	size := len(rects)
+	res := make([]int, 1, size*2)
+	xMap := make(map[int]bool, size*2)
+
+	for _, r := range rects {
+		xMap[r[0]] = true
+		xMap[r[2]] = true
+	}
+
+	for k := range xMap {
+		res = append(res, k)
+	}
+
+	return res
 }

Algorithms/0850.rectangle-area-ii/rectangle-area-ii_test.go

@@ -23,6 +23,11 @@ var tcs = []struct {
 		49,
 	},
 
+	{
+		[][]int{{0, 0, 1000000000, 1000000000}, {0, 1000000000, 1000000000, 2000000000}},
+		98,
+	},
+
 	// 可以有多个 testcase
 }