Merge pull request #1172 from 0xff-dev/2999

Add solution and test-cases for problem 2999

Author: 6boris

Diff for: leetcode/2901-3000/2999.Count-the-Number-of-Powerful-Integers/README.md

@@ -1,28 +1,39 @@
 # [2999.Count the Number of Powerful Integers][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 three integers `start`, `finish`, and `limit`. You are also given a **0-indexed** string `s` representing a **positive** integer.
+
+A **positive** integer `x` is called **powerful** if it ends with `s` (in other words, `s` is a **suffix** of `x`) and each digit in `x` is at most `limit`.
+
+Return the **total** number of powerful integers in the range `[start..finish]`.
+
+A string `x` is a suffix of a string `y` if and only if `x` is a substring of `y` that starts from some index (**including** `0`) in `y` and extends to the index `y.length - 1`. For example, `25` is a suffix of `5125` whereas `512` is not.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: start = 1, finish = 6000, limit = 4, s = "124"
+Output: 5
+Explanation: The powerful integers in the range [1..6000] are 124, 1124, 2124, 3124, and, 4124. All these integers have each digit <= 4, and "124" as a suffix. Note that 5124 is not a powerful integer because the first digit is 5 which is greater than 4.
+It can be shown that there are only 5 powerful integers in this range.
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Count the Number of Powerful Integers
-```go
 ```
+Input: start = 15, finish = 215, limit = 6, s = "10"
+Output: 2
+Explanation: The powerful integers in the range [15..215] are 110 and 210. All these integers have each digit <= 6, and "10" as a suffix.
+It can be shown that there are only 2 powerful integers in this range.
+```
+
+**Example 3:**
 
+```
+Input: start = 1000, finish = 2000, limit = 4, s = "3000"
+Output: 0
+Explanation: All integers in the range [1000..2000] are smaller than 3000, hence "3000" cannot be a suffix of any integer in this range.
+```
 
 ## 结语
 

Diff for: leetcode/2901-3000/2999.Count-the-Number-of-Powerful-Integers/Solution.go

@@ -1,5 +1,55 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import (
+	"fmt"
+	"strings"
+)
+
+func Solution(start int64, finish int64, limit int, s string) int64 {
+	low := fmt.Sprintf("%d", start)
+	high := fmt.Sprintf("%d", finish)
+	n := len(high)
+	low = strings.Repeat("0", n-len(low)) + low // align digits
+	pre_len := n - len(s)                       // prefix length
+	memo := make([]int64, n)
+	for i := range memo {
+		memo[i] = -1
+	}
+
+	var dfs func(int, bool, bool) int64
+	dfs = func(i int, limit_low, limit_high bool) int64 {
+		// recursive boundary
+		if i == n {
+			return 1
+		}
+		if !limit_low && !limit_high && memo[i] != -1 {
+			return memo[i]
+		}
+		lo := 0
+		if limit_low {
+			lo = int(low[i] - '0')
+		}
+		hi := 9
+		if limit_high {
+			hi = int(high[i] - '0')
+		}
+
+		var res int64 = 0
+		if i < pre_len {
+			for digit := lo; digit <= min(hi, limit); digit++ {
+				res += dfs(i+1, limit_low && digit == lo, limit_high && digit == hi)
+			}
+		} else {
+			x := int(s[i-pre_len] - '0')
+			if lo <= x && x <= min(hi, limit) {
+				res = dfs(i+1, limit_low && x == lo, limit_high && x == hi)
+			}
+		}
+
+		if !limit_low && !limit_high {
+			memo[i] = res
+		}
+		return res
+	}
+	return dfs(0, true, true)
 }

Diff for: leetcode/2901-3000/2999.Count-the-Number-of-Powerful-Integers/Solution_test.go

@@ -9,31 +9,33 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name          string
+		start, finish int64
+		limit         int
+		s             string
+		expect        int64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 1, 6000, 4, "124", 5},
+		{"TestCase2", 15, 215, 6, "10", 2},
+		{"TestCase3", 1000, 2000, 4, "3000", 0},
 	}
 
 	//	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.start, c.finish, c.limit, c.s)
 			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.start, c.finish, c.limit, c.s)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }