Add solution and test-cases for problem 2563

leetcode/2501-2600/2563.Count-the-Number-of-Fair-Pairs/README.md

@@ -0,0 +1,33 @@
+# [2563.Count the Number of Fair Pairs][title]
+
+## Description
+Given a **0-indexed** integer array `nums` of size `n` and two integers `lower` and `upper`, return the number of fair pairs.
+
+A pair `(i, j)` is **fair** if:
+
+- `0 <= i < j < n`, and
+- `lower <= nums[i] + nums[j] <= upper`
+
+
+**Example 1:**
+
+```
+Input: nums = [0,1,7,4,4,5], lower = 3, upper = 6
+Output: 6
+Explanation: There are 6 fair pairs: (0,3), (0,4), (0,5), (1,3), (1,4), and (1,5).
+```
+
+**Example 2:**
+
+```
+Input: nums = [1,7,9,2,5], lower = 11, upper = 11
+Output: 1
+Explanation: There is a single fair pair: (2,3).
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/count-the-number-of-fair-pairs
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/2501-2600/2563.Count-the-Number-of-Fair-Pairs/Solution.go

@@ -1,5 +1,27 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "sort"
+
+func Solution(nums []int, lower, upper int) int64 {
+	sort.Ints(nums)
+	var ans int64 = 0
+	l := len(nums)
+	for i := 0; i < len(nums); i++ {
+		// 1, 2, 3, 4
+		tmpL := l - i - 1
+		leftIndex := sort.Search(tmpL, func(ii int) bool {
+			return nums[i]+nums[ii+1+i] >= lower
+		})
+		if leftIndex == tmpL {
+			continue
+		}
+		rightIndex := sort.Search(tmpL, func(ii int) bool {
+			return nums[i]+nums[ii+1+i] > upper
+		})
+		if rightIndex == tmpL && nums[i]+nums[l-1] > upper {
+			continue
+		}
+		ans += int64(rightIndex - leftIndex)
+	}
+	return ans
 }

leetcode/2501-2600/2563.Count-the-Number-of-Fair-Pairs/Solution_test.go

@@ -10,30 +10,30 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		nums   []int
+		l, p   int
+		expect int64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{0, 1, 7, 4, 4, 5}, 3, 6, 6},
+		{"TestCase2", []int{1, 7, 9, 2, 5}, 11, 11, 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.nums, c.l, c.p)
 			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",
+					c.expect, got, c.nums, c.l, c.p)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }