Add solution and test-cases for problem 357

Author: 0xff-dev

leetcode/301-400/0357.Count-Numbers-with-Unique-Digits/README.md

@@ -1,28 +1,23 @@
 # [357.Count Numbers with Unique Digits][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
+Given an integer `n`, return the count of all numbers with unique digits, `x`, where 0 <= x < 10<sup>n</sup>.
+
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 2
+Output: 91
+Explanation: The answer should be the total numbers in the range of 0 ≤ x < 100, excluding 11,22,33,44,55,66,77,88,99
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Count Numbers with Unique Digits
-```go
 ```
-
+Input: n = 0
+Output: 1
+```
 
 ## 结语
 

leetcode/301-400/0357.Count-Numbers-with-Unique-Digits/Solution.go

@@ -1,5 +1,24 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+/*
+
+1: 10
+        末尾是0
+2: 10 + 1*9 + 8*9 = 91
+        末尾是0   末尾非0，
+3: 91 + 1*9*8 +   9*8*8 = 739
+
+4: 739 + 1*9*8*7 +  9*8*8*7 = 5275
+*/
+func Solution(n int) int {
+	ans := make([]int, 9)
+	ans[0], ans[1] = 1, 10
+	base1, base2 := 1, 8
+	for idx := 2; idx <= 8; idx++ {
+		diff := 11 - idx
+		base1 *= diff
+		base2 *= diff
+		ans[idx] = ans[idx-1] + base1 + base2
+	}
+	return ans[n]
 }

leetcode/301-400/0357.Count-Numbers-with-Unique-Digits/Solution_test.go

@@ -10,12 +10,14 @@ 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", 0, 1},
+		{"TestCase2", 2, 91},
+		{"TestCase3", 3, 739},
+		{"TestCase4", 4, 5275},
+		{"TestCase5", 8, 2345851},
 	}
 
 	//	开始测试