Merge pull request #1068 from 0xff-dev/923

Add solution and test-cases for problem 923

Author: 6boris

leetcode/901-1000/0923.3Sum-With-Multiplicity/README.md

@@ -1,28 +1,41 @@
 # [923.3Sum With Multiplicity][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
+Given an integer array `arr`, and an integer `target`, return the number of tuples `i, j, k` such that `i < j < k` and `arr[i] + arr[j] + arr[k] == target`.
+
+As the answer can be very large, return it **modulo** `10^9 + 7`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: arr = [1,1,2,2,3,3,4,4,5,5], target = 8
+Output: 20
+Explanation: 
+Enumerating by the values (arr[i], arr[j], arr[k]):
+(1, 2, 5) occurs 8 times;
+(1, 3, 4) occurs 8 times;
+(2, 2, 4) occurs 2 times;
+(2, 3, 3) occurs 2 times.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-3Sum With Multiplicity
-```go
+```
+Input: arr = [1,1,2,2,2,2], target = 5
+Output: 12
+Explanation: 
+arr[i] = 1, arr[j] = arr[k] = 2 occurs 12 times:
+We choose one 1 from [1,1] in 2 ways,
+and two 2s from [2,2,2,2] in 6 ways.
 ```
 
+**Example 3:**
+
+```
+Input: arr = [2,1,3], target = 6
+Output: 1
+Explanation: (1, 2, 3) occured one time in the array so we return 1.
+```
 
 ## 结语
 

leetcode/901-1000/0923.3Sum-With-Multiplicity/Solution.go

@@ -1,5 +1,25 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+const mod923 = 1000000007
+
+func Solution(arr []int, target int) int {
+	dp := make([][101]int, len(arr))
+	dp[0][arr[0]] = 1
+	for i := 1; i < len(arr); i++ {
+		for j := 0; j < 101; j++ {
+			dp[i][j] = dp[i-1][j]
+		}
+		dp[i][arr[i]]++
+	}
+
+	ans := 0
+	for i := 2; i < len(arr); i++ {
+		cur := arr[i]
+		for pre := i - 1; pre > 0; pre-- {
+			if diff := target - arr[pre] - cur; diff >= 0 && diff <= 100 {
+				ans = (ans + dp[pre-1][diff]) % mod923
+			}
+		}
+	}
+	return ans
 }

leetcode/901-1000/0923.3Sum-With-Multiplicity/Solution_test.go

@@ -10,30 +10,31 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs []int
+		target int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, 1, 2, 2, 3, 3, 4, 4, 5, 5}, 8, 20},
+		{"TestCase2", []int{1, 1, 2, 2, 2, 2}, 5, 12},
+		{"TestCase3", []int{2, 1, 3}, 6, 1},
 	}
 
 	//	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.inputs, c.target)
 			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.inputs, c.target)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }