From e599554c23e1695b943eb5a43f76927df6e124c4 Mon Sep 17 00:00:00 2001
From: 0xff-dev <stevenshuang521@gmail.com>
Date: Tue, 27 Aug 2024 09:03:18 +0800
Subject: [PATCH] Add solution and test-cases for problem 398

---
 .../301-400/0398.Random-Pick-Index/README.md  | 34 ++++++++--------
 .../0398.Random-Pick-Index/Solution.go        | 39 ++++++++++++++++++-
 .../0398.Random-Pick-Index/Solution_test.go   | 20 +++++-----
 3 files changed, 63 insertions(+), 30 deletions(-)

diff --git a/leetcode/301-400/0398.Random-Pick-Index/README.md b/leetcode/301-400/0398.Random-Pick-Index/README.md
index c8b7d18e6..34d77b2f8 100644
--- a/leetcode/301-400/0398.Random-Pick-Index/README.md
+++ b/leetcode/301-400/0398.Random-Pick-Index/README.md
@@ -1,28 +1,28 @@
 # [398.Random Pick Index][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 `nums` with possible **duplicates**, randomly output the index of a given `targett` number. You can assume that the given target number must exist in the array.
 
-**Example 1:**
-
-```
-Input: a = "11", b = "1"
-Output: "100"
-```
+Implement the `Solution` class:
 
-## 题意
-> ...
+- `Solution(int[] nums)` Initializes the object with the array `nums`.
+- `int pick(int target)` Picks a random index `i` from `nums` where `nums[i] == target`. If there are multiple valid i's, then each index should have an equal probability of returning.
 
-## 题解
+**Example 1:**
 
-### 思路1
-> ...
-Random Pick Index
-```go
 ```
-
+Input
+["Solution", "pick", "pick", "pick"]
+[[[1, 2, 3, 3, 3]], [3], [1], [3]]
+Output
+[null, 4, 0, 2]
+
+Explanation
+Solution solution = new Solution([1, 2, 3, 3, 3]);
+solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
+solution.pick(1); // It should return 0. Since in the array only nums[0] is equal to 1.
+solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
+```
 
 ## 结语
 
diff --git a/leetcode/301-400/0398.Random-Pick-Index/Solution.go b/leetcode/301-400/0398.Random-Pick-Index/Solution.go
index d115ccf5e..fb4c3a73e 100644
--- a/leetcode/301-400/0398.Random-Pick-Index/Solution.go
+++ b/leetcode/301-400/0398.Random-Pick-Index/Solution.go
@@ -1,5 +1,40 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+type item398 struct {
+	index int
+	list  []int
+}
+
+type Solution1 struct {
+	data map[int]item398
+}
+
+func Constructor(nums []int) Solution1 {
+	s := Solution1{data: make(map[int]item398)}
+	for i, n := range nums {
+		if _, ok := s.data[n]; !ok {
+			s.data[n] = item398{}
+		}
+		l := s.data[n]
+		l.list = append(l.list, i)
+		s.data[n] = l
+	}
+	return s
+}
+
+func (this *Solution1) Pick(target int) int {
+	v := this.data[target]
+	cur := v.index
+	v.index = (v.index + 1) % len(v.list)
+	this.data[target] = v
+	return this.data[target].list[cur]
+}
+
+func Solution(nums []int, check []int) []int {
+	c := Constructor(nums)
+	ans := make([]int, len(check))
+	for i, n := range check {
+		ans[i] = c.Pick(n)
+	}
+	return ans
 }
diff --git a/leetcode/301-400/0398.Random-Pick-Index/Solution_test.go b/leetcode/301-400/0398.Random-Pick-Index/Solution_test.go
index 14ff50eb4..bdcc6bf9f 100644
--- a/leetcode/301-400/0398.Random-Pick-Index/Solution_test.go
+++ b/leetcode/301-400/0398.Random-Pick-Index/Solution_test.go
@@ -9,31 +9,29 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name        string
+		nums, check []int
+		expect      []int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, 2, 3, 3, 3}, []int{3, 1, 3}, []int{2, 0, 3}},
 	}
 
 	//	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.check)
 			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.nums, c.check)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }