Merge pull request #1556 from 0xff-dev/1840

Add solution and test-cases for problem 1840

Author: 6boris

leetcode/1801-1900/1840.Maximum-Building-Height/1.png

@@ -1,28 +1,52 @@
 # [1840.Maximum Building Height][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 want to build `n` new buildings in a city. The new buildings will be built in a line and are labeled from `1` to `n`.
+
+However, there are city restrictions on the heights of the new buildings:
+
+- The height of each building must be a non-negative integer.
+- The height of the first building **must** be `0`.
+- The height difference between any two adjacent buildings **cannot exceed** `1`.
+
+Additionally, there are city restrictions on the maximum height of specific buildings. These restrictions are given as a 2D integer array `restrictions` where `restrictions[i] = [idi, maxHeighti]` indicates that building `idi` must have a height **less than or equal to** `maxHeighti`.
+
+It is guaranteed that each building will appear **at most once** in `restrictions`, and building `1` will **not** be in `restrictions`.
+
+Return the **maximum possible height** of the **tallest** building.
 
-**Example 1:**
+**Example 1:**  
+
+![1](./1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 5, restrictions = [[2,1],[4,1]]
+Output: 2
+Explanation: The green area in the image indicates the maximum allowed height for each building.
+We can build the buildings with heights [0,1,2,1,2], and the tallest building has a height of 2.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./2.png)
 
-### 思路1
-> ...
-Maximum Building Height
-```go
 ```
+Input: n = 6, restrictions = []
+Output: 5
+Explanation: The green area in the image indicates the maximum allowed height for each building.
+We can build the buildings with heights [0,1,2,3,4,5], and the tallest building has a height of 5.
+```
+
+**Example 3:**  
 
+![3](./3.png)
+
+```
+Input: n = 10, restrictions = [[5,3],[2,5],[7,4],[10,3]]
+Output: 5
+Explanation: The green area in the image indicates the maximum allowed height for each building.
+We can build the buildings with heights [0,1,2,3,3,4,4,5,4,3], and the tallest building has a height of 5.
+```
 
 ## 结语
 

leetcode/1801-1900/1840.Maximum-Building-Height/2.png

@@ -1,5 +1,43 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "sort"
+
+func Solution(n int, restrictions [][]int) int {
+	restrictions = append(restrictions, []int{1, 0})
+
+	sort.Slice(restrictions, func(i, j int) bool {
+		return restrictions[i][0] < restrictions[j][0]
+	})
+
+	m := len(restrictions)
+
+	for i := 1; i < m; i++ {
+		dist := restrictions[i][0] - restrictions[i-1][0]
+		if restrictions[i][1] > restrictions[i-1][1]+dist {
+			restrictions[i][1] = restrictions[i-1][1] + dist
+		}
+	}
+
+	for i := m - 2; i >= 0; i-- {
+		dist := restrictions[i+1][0] - restrictions[i][0]
+		if restrictions[i][1] > restrictions[i+1][1]+dist {
+			restrictions[i][1] = restrictions[i+1][1] + dist
+		}
+	}
+
+	ret := 0
+
+	for i := 0; i < m-1; i++ {
+		id1, h1 := restrictions[i][0], restrictions[i][1]
+		id2, h2 := restrictions[i+1][0], restrictions[i+1][1]
+
+		peak := (h1 + h2 + (id2 - id1)) / 2
+		ret = max(ret, peak)
+	}
+
+	lastId := restrictions[m-1][0]
+	lastH := restrictions[m-1][1]
+	ret = max(ret, lastH+(n-lastId))
+
+	return ret
 }

leetcode/1801-1900/1840.Maximum-Building-Height/3.png

@@ -9,22 +9,23 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name         string
+		n            int
+		restrictions [][]int
+		expect       int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 5, [][]int{{2, 1}, {4, 1}}, 2},
+		{"TestCase2", 6, [][]int{}, 5},
+		{"TestCase3", 10, [][]int{{5, 3}, {2, 5}, {7, 4}, {10, 3}}, 5},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.n, c.restrictions)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v",
+					c.expect, got, c.n, c.restrictions)
 			}
 		})
 	}