Add solution and test-cases for problem 2434

leetcode/2401-2500/2434.Using-a-Robot-to-Print-the-Lexicographically-Smallest-String/README.md

@@ -1,28 +1,46 @@
 # [2434.Using a Robot to Print the Lexicographically Smallest String][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 string `s` and a robot that currently holds an empty string `t`. Apply one of the following operations until `t` and `t` **are both empty**:
+
+- Remove the **first** character of a string `s` and give it to the robot. The robot will append this character to the string `t`.
+- Remove the **last** character of a string `t` and give it to the robot. The robot will write this character on paper.
+
+Return the lexicographically smallest string that can be written on the paper.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: s = "zza"
+Output: "azz"
+Explanation: Let p denote the written string.
+Initially p="", s="zza", t="".
+Perform first operation three times p="", s="", t="zza".
+Perform second operation three times p="azz", s="", t="".
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Using a Robot to Print the Lexicographically Smallest String
-```go
 ```
+Input: s = "bac"
+Output: "abc"
+Explanation: Let p denote the written string.
+Perform first operation twice p="", s="c", t="ba". 
+Perform second operation twice p="ab", s="c", t="". 
+Perform first operation p="ab", s="", t="c". 
+Perform second operation p="abc", s="", t="".
+```
+
+**Example 3:**
 
+```
+Input: s = "bdda"
+Output: "addb"
+Explanation: Let p denote the written string.
+Initially p="", s="bdda", t="".
+Perform first operation four times p="", s="", t="bdda".
+Perform second operation four times p="addb", s="", t="".
+```
 
 ## 结语
 

leetcode/2401-2500/2434.Using-a-Robot-to-Print-the-Lexicographically-Smallest-String/Solution.go

@@ -1,5 +1,25 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(s string) string {
+	cnt := make([]int, 26)
+	for _, c := range s {
+		cnt[c-'a']++
+	}
+
+	stack := []rune{}
+	res := []rune{}
+	minCharacter := 'a'
+	for _, c := range s {
+		stack = append(stack, c)
+		cnt[c-'a']--
+		for minCharacter != 'z' && cnt[minCharacter-'a'] == 0 {
+			minCharacter++
+		}
+		for len(stack) > 0 && stack[len(stack)-1] <= minCharacter {
+			res = append(res, stack[len(stack)-1])
+			stack = stack[:len(stack)-1]
+		}
+	}
+
+	return string(res)
 }

leetcode/2401-2500/2434.Using-a-Robot-to-Print-the-Lexicographically-Smallest-String/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 string
+		expect string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", "zza", "azz"},
+		{"TestCase2", "bac", "abc"},
+		{"TestCase3", "bdda", "addb"},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ 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() {
 }