Merge pull request #647 from 0xff-dev/454

Add solution and test-cases for problem 454

leetcode/401-500/0454.4Sum-II/README.md

@@ -1,28 +1,28 @@
 # [454.4Sum 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
+Given four integer arrays `nums1`, `nums2`, `nums3`, and `nums4` all of length `n`, return the number of tuples (`i, j, k, l`) such that:
+
+- `0 <= i, j, k, l < n`
+- `nums1[i] + nums2[j] + nums3[k] + nums4[l] == 0`
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums1 = [1,2], nums2 = [-2,-1], nums3 = [-1,2], nums4 = [0,2]
+Output: 2
+Explanation:
+The two tuples are:
+1. (0, 0, 0, 1) -> nums1[0] + nums2[0] + nums3[0] + nums4[1] = 1 + (-2) + (-1) + 2 = 0
+2. (1, 1, 0, 0) -> nums1[1] + nums2[1] + nums3[0] + nums4[0] = 2 + (-1) + (-1) + 0 = 0
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-4Sum II
-```go
 ```
-
+Input: nums1 = [0], nums2 = [0], nums3 = [0], nums4 = [0]
+Output: 1
+```
 
 ## 结语
 

leetcode/401-500/0454.4Sum-II/Solution.go

@@ -1,5 +1,21 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(nums1 []int, nums2 []int, nums3 []int, nums4 []int) int {
+	l := len(nums1)
+	cache := make(map[int]int)
+	for i := 0; i < l; i++ {
+		for j := 0; j < l; j++ {
+			cache[nums1[i]+nums2[j]]++
+		}
+	}
+	ans := 0
+	for i := 0; i < l; i++ {
+		for j := 0; j < l; j++ {
+			target := 0 - nums3[i] - nums4[j]
+			if v, ok := cache[target]; ok {
+				ans += v
+			}
+		}
+	}
+	return ans
 }

leetcode/401-500/0454.4Sum-II/Solution_test.go

@@ -9,31 +9,30 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name           string
+		n1, n2, n3, n4 []int
+		expect         int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, 2}, []int{-2, -1}, []int{-1, 2}, []int{0, 2}, 2},
+		{"TestCase2", []int{0}, []int{0}, []int{0}, []int{0}, 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.n1, c.n2, c.n3, c.n4)
 			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 %v %v",
+					c.expect, got, c.n1, c.n2, c.n3, c.n4)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }