Merge pull request #1251 from 0xff-dev/3307

Add solution and test-cases for problem 3307

Author: 6boris

leetcode/3301-3400/3307.Find-the-K-th-Character-in-String-Game-II/README.md

@@ -1,28 +1,51 @@
 # [3307.Find the K-th Character in String Game II][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
+Alice and Bob are playing a game. Initially, Alice has a string `word = "a"`.
+
+You are given a **positive** integer k. You are also given an integer array `operations`, where `operations[i]` represents the **type** of the `ith` operation.
+
+Now Bob will ask Alice to perform **all** operations in sequence:
+
+- If `operations[i] == 0`, **append** a copy of `word` to itself.
+- If `operations[i] == 1`, generate a new string by **changing** each character in `word` to its **next** character in the English alphabet, and **append** it to the original `word`. For example, performing the operation on `"c"` generates `"cd"` and performing the operation on `"zb"` generates `"zbac"`.
+
+Return the value of the `kth` character in `word` after performing all the operations.
+
+**Note** that the character `'z'` can be changed to `'a'` in the second type of operation.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
-```
+Input: k = 5, operations = [0,0,0]
+
+Output: "a"
 
-## 题意
-> ...
+Explanation:
 
-## 题解
+Initially, word == "a". Alice performs the three operations as follows:
 
-### 思路1
-> ...
-Find the K-th Character in String Game II
-```go
+Appends "a" to "a", word becomes "aa".
+Appends "aa" to "aa", word becomes "aaaa".
+Appends "aaaa" to "aaaa", word becomes "aaaaaaaa".
 ```
 
+**Example 2:**
+
+```
+Input: k = 10, operations = [0,1,0,1]
+
+Output: "b"
+
+Explanation:
+
+Initially, word == "a". Alice performs the four operations as follows:
+
+Appends "a" to "a", word becomes "aa".
+Appends "bb" to "aa", word becomes "aabb".
+Appends "aabb" to "aabb", word becomes "aabbaabb".
+Appends "bbccbbcc" to "aabbaabb", word becomes "aabbaabbbbccbbcc".
+```
 
 ## 结语
 

leetcode/3301-3400/3307.Find-the-K-th-Character-in-String-Game-II/Solution.go

@@ -1,5 +1,18 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "math/bits"
+
+func Solution(k int64, operations []int) byte {
+	ans := 0
+	for k != 1 {
+		t := bits.Len64(uint64(k)) - 1
+		if (1 << t) == k {
+			t--
+		}
+		k -= (1 << t)
+		if operations[t] != 0 {
+			ans++
+		}
+	}
+	return byte('a' + (ans % 26))
 }

leetcode/3301-3400/3307.Find-the-K-th-Character-in-String-Game-II/Solution_test.go

@@ -9,31 +9,31 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name       string
+		k          int64
+		operations []int
+		expect     byte
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 5, []int{0, 0, 0}, 'a'},
+		{"TestCase2", 10, []int{0, 1, 0, 1}, 'b'},
 	}
 
 	//	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.k, c.operations)
 			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.k, c.operations)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }