Add solution and test-cases for problem 738

Author: 0xff-dev

leetcode/701-800/0738.Monotone-Increasing-Digits/README.md

@@ -1,28 +1,30 @@
 # [738.Monotone Increasing 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
+An integer has **monotone increasing digits** if and only if each pair of adjacent digits `x` and `y` satisfy `x <= y`.
+
+Given an integer `n`, return the largest number that is less than or equal to `n` with **monotone increasing digits**.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 10
+Output: 9
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Monotone Increasing Digits
-```go
+```
+Input: n = 1234
+Output: 1234
 ```
 
+**Example 3:**
+
+```
+Input: n = 332
+Output: 299
+```
 
 ## 结语
 

leetcode/701-800/0738.Monotone-Increasing-Digits/Solution.go

@@ -1,5 +1,32 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "fmt"
+
+func Solution(n int) int {
+	ns := []byte(fmt.Sprintf("%d", n))
+	idx := 1
+	for ; idx < len(ns); idx++ {
+		if ns[idx] < ns[idx-1] {
+			break
+		}
+	}
+	if idx != len(ns) {
+		index := idx - 1
+		top := ns[index]
+		pre := index - 1
+		for ; pre >= 0 && ns[pre] == top; pre-- {
+			ns[pre] = '9'
+		}
+		ns[index] = '9'
+		ns[pre+1] = top - 1
+		for ; idx < len(ns); idx++ {
+			ns[idx] = '9'
+		}
+	}
+
+	ans := 0
+	for i := 0; i < len(ns); i++ {
+		ans = ans*10 + int(ns[i]-'0')
+	}
+	return ans
 }

leetcode/701-800/0738.Monotone-Increasing-Digits/Solution_test.go

@@ -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", 10, 9},
+		{"TestCase2", 1234, 1234},
+		{"TestCase3", 332, 299},
 	}
 
 	//	开始测试
@@ -30,10 +30,11 @@ 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() {
+
 }