Add solution and test-cases for problem 935

leetcode/901-1000/0935.Knight-Dialer/README.md

@@ -1,28 +1,45 @@
 # [935.Knight Dialer][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
+The chess knight has a **unique movement**, it may move two squares vertically and one square horizontally, or two squares horizontally and one square vertically (with both forming the shape of an **L**). The possible movements of chess knight are shown in this diagaram:
+
+A chess knight can move as indicated in the chess diagram below:
+
+![chess](./chess.jpeg)
+
+We have a chess knight and a phone pad as shown below, the knight **can only stand on a numeric cell** (i.e. blue cell).
+
+![phone](./phone.jpeg)
+
+Given an integer n, return how many distinct phone numbers of length `n` we can dial.
+
+You are allowed to place the knight **on any numeric cell** initially and then you should perform `n - 1` jumps to dial a number of length `n`. All jumps should be **valid** knight jumps.
+
+As the answer may be very large, **return the answer modulo** `10^9 + 7`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 1
+Output: 10
+Explanation: We need to dial a number of length 1, so placing the knight over any numeric cell of the 10 cells is sufficient.
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Knight Dialer
-```go
+```
+Input: n = 2
+Output: 20
+Explanation: All the valid number we can dial are [04, 06, 16, 18, 27, 29, 34, 38, 40, 43, 49, 60, 61, 67, 72, 76, 81, 83, 92, 94]
 ```
 
+**Example 3:**
+
+```
+Input: n = 3131
+Output: 136006598
+Explanation: Please take care of the mod.
+```
 
 ## 结语
 

leetcode/901-1000/0935.Knight-Dialer/Solution.go

@@ -1,5 +1,44 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+const mod935 = 1000000007
+
+func Solution(n int) int {
+	nexts := map[int][]int{
+		1: {6, 8},
+		2: {7, 9},
+		3: {4, 8},
+		4: {0, 3, 9},
+		6: {0, 1, 7},
+		7: {2, 6},
+		8: {1, 3},
+		9: {4, 2},
+		0: {4, 6},
+	}
+	cache := make(map[int]map[int]int)
+	for i := 0; i <= 9; i++ {
+		cache[i] = make(map[int]int)
+		cache[i][1] = 1
+	}
+	var dfs func(int, int) int
+	dfs = func(num, nn int) int {
+		v, ok := cache[num]
+		if ok {
+			vv, ok1 := v[nn]
+			if ok1 {
+				return vv
+			}
+		}
+		ans := 0
+		for _, next := range nexts[num] {
+			ans = (ans + dfs(next, nn-1)) % mod935
+		}
+		cache[num][nn] = ans
+		return ans
+	}
+	ans := 0
+	for i := 0; i <= 9; i++ {
+		a := dfs(i, n) % mod935
+		ans = (ans + a) % mod935
+	}
+	return ans
 }

leetcode/901-1000/0935.Knight-Dialer/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", 1, 10},
+		{"TestCase2", 2, 20},
+		{"TestCase3", 3, 46},
+		{"TestCase4", 20, 58689536},
+		{"TestCase5", 3131, 136006598},
 	}
 
 	//	开始测试
@@ -30,10 +32,10 @@ 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() {
 }