Add solution 1846

Author: halfrost

leetcode/0218.The-Skyline-Problem/218. The Skyline Problem.go

@@ -81,7 +81,7 @@ func (bit *BinaryIndexedTree) Query(index int) int {
 	return sum
 }
 
-// 解法三 线段树 Segment Tree，时间复杂度 O(n log n)
+// 解法二 线段树 Segment Tree，时间复杂度 O(n log n)
 func getSkyline1(buildings [][]int) [][]int {
 	st, ans, lastHeight, check := template.SegmentTree{}, [][]int{}, 0, false
 	posMap, pos := discretization218(buildings)

leetcode/1846.Maximum-Element-After-Decreasing-and-Rearranging/1846. Maximum Element After Decreasing and Rearranging.go

@@ -0,0 +1,25 @@
+package leetcode
+
+func maximumElementAfterDecrementingAndRearranging(arr []int) int {
+	n := len(arr)
+	cnt := make([]int, n+1)
+	for _, v := range arr {
+		cnt[min(v, n)]++
+	}
+	miss := 0
+	for _, c := range cnt[1:] {
+		if c == 0 {
+			miss++
+		} else {
+			miss -= min(c-1, miss)
+		}
+	}
+	return n - miss
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}

leetcode/1846.Maximum-Element-After-Decreasing-and-Rearranging/1846. Maximum Element After Decreasing and Rearranging_test.go

@@ -0,0 +1,52 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question1846 struct {
+	para1846
+	ans1846
+}
+
+// para 是参数
+// one 代表第一个参数
+type para1846 struct {
+	arr []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans1846 struct {
+	one int
+}
+
+func Test_Problem1846(t *testing.T) {
+
+	qs := []question1846{
+
+		{
+			para1846{[]int{2, 2, 1, 2, 1}},
+			ans1846{2},
+		},
+
+		{
+			para1846{[]int{100, 1, 1000}},
+			ans1846{3},
+		},
+
+		{
+			para1846{[]int{1, 2, 3, 4, 5}},
+			ans1846{5},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 1846------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans1846, q.para1846
+		fmt.Printf("【input】:%v       【output】:%v\n", p, maximumElementAfterDecrementingAndRearranging(p.arr))
+	}
+	fmt.Printf("\n\n\n")
+}

leetcode/1846.Maximum-Element-After-Decreasing-and-Rearranging/README.md

@@ -0,0 +1,103 @@
+# [1846. Maximum Element After Decreasing and Rearranging](https://leetcode.com/problems/maximum-element-after-decreasing-and-rearranging/)
+
+
+## 题目
+
+You are given an array of positive integers `arr`. Perform some operations (possibly none) on `arr` so that it satisfies these conditions:
+
+- The value of the **first** element in `arr` must be `1`.
+- The absolute difference between any 2 adjacent elements must be **less than or equal to** `1`. In other words, `abs(arr[i] - arr[i - 1]) <= 1` for each `i` where `1 <= i < arr.length` (**0-indexed**). `abs(x)` is the absolute value of `x`.
+
+There are 2 types of operations that you can perform any number of times:
+
+- **Decrease** the value of any element of `arr` to a **smaller positive integer**.
+- **Rearrange** the elements of `arr` to be in any order.
+
+Return *the **maximum** possible value of an element in* `arr` *after performing the operations to satisfy the conditions*.
+
+**Example 1:**
+
+```
+Input: arr = [2,2,1,2,1]
+Output: 2
+Explanation:
+We can satisfy the conditions by rearrangingarr so it becomes[1,2,2,2,1].
+The largest element inarr is 2.
+
+```
+
+**Example 2:**
+
+```
+Input: arr = [100,1,1000]
+Output: 3
+Explanation:
+One possible way to satisfy the conditions is by doing the following:
+1. Rearrangearr so it becomes[1,100,1000].
+2. Decrease the value of the second element to 2.
+3. Decrease the value of the third element to 3.
+Nowarr = [1,2,3], whichsatisfies the conditions.
+The largest element inarr is 3.
+```
+
+**Example 3:**
+
+```
+Input: arr = [1,2,3,4,5]
+Output: 5
+Explanation: The array already satisfies the conditions, and the largest element is 5.
+
+```
+
+**Constraints:**
+
+- `1 <= arr.length <= 10^5`
+- `1 <= arr[i] <= 10^9`
+
+## 题目大意
+
+给你一个正整数数组 arr 。请你对 arr 执行一些操作（也可以不进行任何操作），使得数组满足以下条件：
+
+- arr 中 第一个 元素必须为 1 。
+- 任意相邻两个元素的差的绝对值 小于等于 1 ，也就是说，对于任意的 1 <= i < arr.length （数组下标从 0 开始），都满足 abs(arr[i] - arr[i - 1]) <= 1 。abs(x) 为 x 的绝对值。
+
+你可以执行以下 2 种操作任意次：
+
+- 减小 arr 中任意元素的值，使其变为一个 更小的正整数 。
+- 重新排列 arr 中的元素，你可以以任意顺序重新排列。
+
+请你返回执行以上操作后，在满足前文所述的条件下，arr 中可能的 最大值 。
+
+## 解题思路
+
+- 正整数数组 arr 第一个元素必须为 1，且两两元素绝对值小于等于 1，那么 arr 最大值肯定不大于 n。采用贪心的策略，先统计所有元素出现的次数，大于 n 的元素出现次数都累加到 n 上。然后从 1 扫描到 n，遇到“空隙”（出现次数为 0 的元素），便将最近一个出现次数大于 1 的元素“挪”过来填补“空隙”。题目所求最大值出现在，“填补空隙”之后，数组从左往右连续的最右端。
+
+## 代码
+
+```go
+package leetcode
+
+func maximumElementAfterDecrementingAndRearranging(arr []int) int {
+	n := len(arr)
+	count := make([]int, n+1)
+	for _, v := range arr {
+		count[min(v, n)]++
+	}
+	miss := 0
+	for _, c := range count[1:] {
+		if c == 0 {
+			miss++
+		} else {
+			miss -= min(c-1, miss)
+		}
+	}
+	return n - miss
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+```

website/content/ChapterFour/0200~0299/0218.The-Skyline-Problem.md

@@ -162,7 +162,7 @@ func (bit *BinaryIndexedTree) Query(index int) int {
 	return sum
 }
 
-// 解法三 线段树 Segment Tree，时间复杂度 O(n log n)
+// 解法二 线段树 Segment Tree，时间复杂度 O(n log n)
 func getSkyline1(buildings [][]int) [][]int {
 	st, ans, lastHeight, check := template.SegmentTree{}, [][]int{}, 0, false
 	posMap, pos := discretization218(buildings)

website/content/ChapterFour/1700~1799/1758.Minimum-Changes-To-Make-Alternating-Binary-String.md

@@ -70,7 +70,8 @@ func min(a, b int) int {
 ```
 
 
-
 ----------------------------------------------
+<div style="display: flex;justify-content: space-between;align-items: center;">
 <p><a href="https://books.halfrost.com/leetcode/ChapterFour/1700~1799/1752.Check-if-Array-Is-Sorted-and-Rotated/">⬅️上一页</a></p>
-
+<p><a href="https://books.halfrost.com/leetcode/ChapterFour/1800~1899/1846.Maximum-Element-After-Decreasing-and-Rearranging/">下一页➡️</a></p>
+</div>

website/content/ChapterFour/1800~1899/1846.Maximum-Element-After-Decreasing-and-Rearranging.md

@@ -0,0 +1,108 @@
+# [1846. Maximum Element After Decreasing and Rearranging](https://leetcode.com/problems/maximum-element-after-decreasing-and-rearranging/)
+
+
+## 题目
+
+You are given an array of positive integers `arr`. Perform some operations (possibly none) on `arr` so that it satisfies these conditions:
+
+- The value of the **first** element in `arr` must be `1`.
+- The absolute difference between any 2 adjacent elements must be **less than or equal to** `1`. In other words, `abs(arr[i] - arr[i - 1]) <= 1` for each `i` where `1 <= i < arr.length` (**0-indexed**). `abs(x)` is the absolute value of `x`.
+
+There are 2 types of operations that you can perform any number of times:
+
+- **Decrease** the value of any element of `arr` to a **smaller positive integer**.
+- **Rearrange** the elements of `arr` to be in any order.
+
+Return *the **maximum** possible value of an element in* `arr` *after performing the operations to satisfy the conditions*.
+
+**Example 1:**
+
+```
+Input: arr = [2,2,1,2,1]
+Output: 2
+Explanation:
+We can satisfy the conditions by rearrangingarr so it becomes[1,2,2,2,1].
+The largest element inarr is 2.
+
+```
+
+**Example 2:**
+
+```
+Input: arr = [100,1,1000]
+Output: 3
+Explanation:
+One possible way to satisfy the conditions is by doing the following:
+1. Rearrangearr so it becomes[1,100,1000].
+2. Decrease the value of the second element to 2.
+3. Decrease the value of the third element to 3.
+Nowarr = [1,2,3], whichsatisfies the conditions.
+The largest element inarr is 3.
+```
+
+**Example 3:**
+
+```
+Input: arr = [1,2,3,4,5]
+Output: 5
+Explanation: The array already satisfies the conditions, and the largest element is 5.
+
+```
+
+**Constraints:**
+
+- `1 <= arr.length <= 10^5`
+- `1 <= arr[i] <= 10^9`
+
+## 题目大意
+
+给你一个正整数数组 arr 。请你对 arr 执行一些操作（也可以不进行任何操作），使得数组满足以下条件：
+
+- arr 中 第一个 元素必须为 1 。
+- 任意相邻两个元素的差的绝对值 小于等于 1 ，也就是说，对于任意的 1 <= i < arr.length （数组下标从 0 开始），都满足 abs(arr[i] - arr[i - 1]) <= 1 。abs(x) 为 x 的绝对值。
+
+你可以执行以下 2 种操作任意次：
+
+- 减小 arr 中任意元素的值，使其变为一个 更小的正整数 。
+- 重新排列 arr 中的元素，你可以以任意顺序重新排列。
+
+请你返回执行以上操作后，在满足前文所述的条件下，arr 中可能的 最大值 。
+
+## 解题思路
+
+- 正整数数组 arr 第一个元素必须为 1，且两两元素绝对值小于等于 1，那么 arr 最大值肯定不大于 n。采用贪心的策略，先统计所有元素出现的次数，大于 n 的元素出现次数都累加到 n 上。然后从 1 扫描到 n，遇到“空隙”（出现次数为 0 的元素），便将最近一个出现次数大于 1 的元素“挪”过来填补“空隙”。题目所求最大值出现在，“填补空隙”之后，数组从左往右连续的最右端。
+
+## 代码
+
+```go
+package leetcode
+
+func maximumElementAfterDecrementingAndRearranging(arr []int) int {
+	n := len(arr)
+	count := make([]int, n+1)
+	for _, v := range arr {
+		count[min(v, n)]++
+	}
+	miss := 0
+	for _, c := range count[1:] {
+		if c == 0 {
+			miss++
+		} else {
+			miss -= min(c-1, miss)
+		}
+	}
+	return n - miss
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+```
+
+
+----------------------------------------------
+<p><a href="https://books.halfrost.com/leetcode/ChapterFour/1700~1799/1758.Minimum-Changes-To-Make-Alternating-Binary-String/">⬅️上一页</a></p>
+

website/content/ChapterFour/1800~1899/_index.md

@@ -0,0 +1,4 @@
+---
+bookCollapseSection: true
+weight: 20
+---