Add solution and test-cases for problem 679

leetcode/601-700/0679.24-Game/README.md

@@ -1,28 +1,38 @@
 # [679.24 Game][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 an integer array `cards` of length `4`. You have four cards, each containing a number in the range `[1, 9]`. You should arrange the numbers on these cards in a mathematical expression using the operators `['+', '-', '*', '/']` and the parentheses `'('` and `')'` to get the value 24.
+
+You are restricted with the following rules:
+
+- The division operator `'/'` represents real division, not integer division.
+
+    - For example, `4 / (1 - 2 / 3) = 4 / (1 / 3) = 12`.
+
+- Every operation done is between two numbers. In particular, we cannot use `'-'` as a unary operator.
+
+    - For example, if `cards = [1, 1, 1, 1]`, the expression `"-1 - 1 - 1 - 1"` is **not allowed**.
+
+- You cannot concatenate numbers together
+
+    - For example, if `cards = [1, 2, 1, 2]`, the expression `"12 + 12"` is not valid.
+
+Return `true` if you can get such expression that evaluates to `24`, and `false` otherwise.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: cards = [4,1,8,7]
+Output: true
+Explanation: (8-4) * (7-1) = 24
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-24 Game
-```go
 ```
-
+Input: cards = [1,2,1,2]
+Output: false
+```
 
 ## 结语
 

leetcode/601-700/0679.24-Game/Solution.go

@@ -1,5 +1,57 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "math"
+
+func Solution(cards []int) bool {
+	nums := make([]float64, len(cards))
+	for i, v := range cards {
+		nums[i] = float64(v)
+	}
+	return dfs(nums)
+}
+
+// 递归函数：判断当前数字数组是否可以通过操作得到24
+func dfs(nums []float64) bool {
+	if len(nums) == 1 {
+		// 终止条件：只有一个数字，判断是否接近24
+		return math.Abs(nums[0]-24) < 1e-6
+	}
+	// 遍历所有两两组合
+	for i := 0; i < len(nums); i++ {
+		for j := i + 1; j < len(nums); j++ {
+			// 取出两个数
+			a, b := nums[i], nums[j]
+			// 剩余的数字
+			rest := make([]float64, 0, len(nums)-1)
+			for k := 0; k < len(nums); k++ {
+				if k != i && k != j {
+					rest = append(rest, nums[k])
+				}
+			}
+
+			// 所有可能的运算
+			operations := [][]float64{
+				{a + b},
+				{a - b},
+				{b - a},
+				{a * b},
+			}
+			// 除法要判断除数不为零
+			if math.Abs(b) > 1e-6 {
+				operations = append(operations, []float64{a / b})
+			}
+			if math.Abs(a) > 1e-6 {
+				operations = append(operations, []float64{b / a})
+			}
+
+			// 递归
+			for _, op := range operations {
+				nextNums := append(rest, op[0])
+				if dfs(nextNums) {
+					return true
+				}
+			}
+		}
+	}
+	return false
 }

leetcode/601-700/0679.24-Game/Solution_test.go

@@ -10,12 +10,11 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
+		inputs []int
 		expect bool
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{4, 1, 8, 7}, true},
+		{"TestCase2", []int{1, 2, 1, 2}, false},
 	}
 
 	//	开始测试
@@ -30,10 +29,10 @@ 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() {
 }