Merge pull request #1302 from 0xff-dev/3027

Add solution and test-cases for problem 3027

Author: 6boris

leetcode/3001-3100/3027.Find-the-Number-of-Ways-to-Place-People-II/1.png

@@ -1,28 +1,58 @@
 # [3027.Find the Number of Ways to Place People II][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+You are given a 2D array `points` of size `n x 2` representing integer coordinates of some points on a 2D-plane, where `points[i] = [xi, yi]`.
+
+We define the **right** direction as positive x-axis (**increasing x-coordinate**) and the **left** direction as negative x-axis (**decreasing x-coordinate**). Similarly, we define the **up** direction as positive y-axis (**increasing y-coordinate**) and the **down** direction as negative y-axis (**decreasing y-coordinate**)
+
+You have to place `n` people, including Alice and Bob, at these points such that there is **exactly one** person at every point. Alice wants to be alone with Bob, so Alice will build a rectangular fence with Alice's position as the **upper left corner** and Bob's position as the **lower right corner** of the fence (**Note** that the fence **might not** enclose any area, i.e. it can be a line). If any person other than Alice and Bob is either **inside** the fence or **on** the fence, Alice will be sad.
+
+Return the number of **pairs of points** where you can place Alice and Bob, such that Alice **does not** become sad on building the fence.
+
+**Note** that Alice can only build a fence with Alice's position as the upper left corner, and Bob's position as the lower right corner. For example, Alice cannot build either of the fences in the picture below with four corners `(1, 1), (1, 3), (3, 1), and (3, 3)`, because:
+
+- With Alice at `(3, 3)` and Bob at `(1, 1)`, Alice's position is not the upper left corner and Bob's position is not the lower right corner of the fence.
+- With Alice at `(1, 3)` and Bob at `(1, 1)`, Bob's position is not the lower right corner of the fence.
+
+![1](./1.png)
 
-**Example 1:**
+
+**Example 1:**  
+
+![2](./2.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: points = [[1,1],[2,2],[3,3]]
+Output: 0
+Explanation: There is no way to place Alice and Bob such that Alice can build a fence with Alice's position as the upper left corner and Bob's position as the lower right corner. Hence we return 0.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![3](./3.png)
 
-### 思路1
-> ...
-Find the Number of Ways to Place People II
-```go
 ```
+Input: points = [[6,2],[4,4],[2,6]]
+Output: 2
+Explanation: There are two ways to place Alice and Bob such that Alice will not be sad:
+- Place Alice at (4, 4) and Bob at (6, 2).
+- Place Alice at (2, 6) and Bob at (4, 4).
+You cannot place Alice at (2, 6) and Bob at (6, 2) because the person at (4, 4) will be inside the fence.
+```
+
+**Example 3:**  
 
+![4](./4.png)
+
+```
+Input: points = [[3,1],[1,3],[1,1]]
+Output: 2
+Explanation: There are two ways to place Alice and Bob such that Alice will not be sad:
+- Place Alice at (1, 1) and Bob at (3, 1).
+- Place Alice at (1, 3) and Bob at (1, 1).
+You cannot place Alice at (1, 3) and Bob at (3, 1) because the person at (1, 1) will be on the fence.
+Note that it does not matter if the fence encloses any area, the first and second fences in the image are valid.
+```
 
 ## 结语
 

leetcode/3001-3100/3027.Find-the-Number-of-Ways-to-Place-People-II/2.png

@@ -1,5 +1,35 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import (
+	"math"
+	"sort"
+)
+
+func Solution(points [][]int) int {
+	ans := 0
+	sort.Slice(points, func(i, j int) bool {
+		if points[i][0] == points[j][0] {
+			return points[i][1] > points[j][1]
+		}
+		return points[i][0] < points[j][0]
+	})
+
+	for i := 0; i < len(points)-1; i++ {
+		pointA := points[i]
+		xMin := pointA[0] - 1
+		xMax := math.MaxInt32
+		yMin := math.MinInt32
+		yMax := pointA[1] + 1
+
+		for j := i + 1; j < len(points); j++ {
+			pointB := points[j]
+			if pointB[0] > xMin && pointB[0] < xMax &&
+				pointB[1] > yMin && pointB[1] < yMax {
+				ans++
+				xMin = pointB[0]
+				yMin = pointB[1]
+			}
+		}
+	}
+	return ans
 }

leetcode/3001-3100/3027.Find-the-Number-of-Ways-to-Place-People-II/3.png

@@ -10,12 +10,12 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{{1, 1}, {2, 2}, {3, 3}}, 0},
+		{"TestCase2", [][]int{{6, 2}, {4, 4}, {2, 6}}, 2},
+		{"TestCase3", [][]int{{3, 1}, {1, 3}, {1, 1}}, 2},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }