Add solution and test-cases for problem 2161

Author: 0xff-dev

leetcode/2101-2200/2161.Partition-Array-According-to-Given-Pivot/README.md

@@ -1,28 +1,37 @@
 # [2161.Partition Array According to Given Pivot][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 **0-indexed** integer array `nums` and an integer `pivot`. Rearrange `nums` such that the following conditions are satisfied:
+
+- Every element less than `pivot` appears **before** every element greater than `pivot`.
+- Every element equal to `pivot` appears **in between** the elements less than and greater than `pivot`.
+- The **relative order** of the elements less than `pivot` and the elements greater than `pivot` is maintained.
+
+    - More formally, consider every `pi`, `pj` where `pi` is the new position of the `ith` element and `pj` is the new position of the `jth` element. For elements less than `pivot`, if `i < j` and `nums[i] < pivot` and `nums[j] < pivot`, then `pi < pj`. Similarly for elements greater than `pivot`, if `i < j` and `nums[i] > pivot` and `nums[j] > pivot`, then `pi < pj`.
+
+Return `nums` after the rearrangement.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums = [9,12,5,10,14,3,10], pivot = 10
+Output: [9,5,3,10,10,12,14]
+Explanation: 
+The elements 9, 5, and 3 are less than the pivot so they are on the left side of the array.
+The elements 12 and 14 are greater than the pivot so they are on the right side of the array.
+The relative ordering of the elements less than and greater than pivot is also maintained. [9, 5, 3] and [12, 14] are the respective orderings.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Partition Array According to Given Pivot
-```go
 ```
-
+Input: nums = [-3,4,3,2], pivot = 2
+Output: [-3,2,4,3]
+Explanation: 
+The element -3 is less than the pivot so it is on the left side of the array.
+The elements 4 and 3 are greater than the pivot so they are on the right side of the array.
+The relative ordering of the elements less than and greater than pivot is also maintained. [-3] and [4, 3] are the respective orderings.
+```
 
 ## 结语
 

leetcode/2101-2200/2161.Partition-Array-According-to-Given-Pivot/Solution.go

@@ -1,5 +1,22 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(nums []int, pivot int) []int {
+	i, j := 0, len(nums)-1
+	res := make([]int, len(nums))
+	for k := 0; k < len(nums); k++ {
+		if nums[k] < pivot {
+			res[i] = nums[k]
+			i++
+		}
+	}
+	for k := len(nums) - 1; k >= 0; k-- {
+		if nums[k] > pivot {
+			res[j] = nums[k]
+			j--
+		}
+	}
+	for ; i <= j; i++ {
+		res[i] = pivot
+	}
+	return res
 }

leetcode/2101-2200/2161.Partition-Array-According-to-Given-Pivot/Solution_test.go

@@ -10,30 +10,30 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		nums   []int
+		pivot  int
+		expect []int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{9, 12, 5, 10, 14, 3, 10}, 10, []int{9, 5, 3, 10, 10, 12, 14}},
+		{"TestCase2", []int{-3, 4, 3, 2}, 2, []int{-3, 2, 4, 3}},
 	}
 
 	//	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.nums, c.pivot)
 			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.nums, c.pivot)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }