From 5eba993b2f5f6ff4daccab77cc95ffffb4ca879d Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Thu, 9 May 2024 07:49:08 +0100
Subject: [PATCH] Swift Implementation for LCCI 17.06
---
lcci/17.06.Number Of 2s In Range/README.md | 39 +++++++++++++++++++
lcci/17.06.Number Of 2s In Range/README_EN.md | 39 +++++++++++++++++++
.../Solution.swift | 36 +++++++++++++++++
3 files changed, 114 insertions(+)
create mode 100644 lcci/17.06.Number Of 2s In Range/Solution.swift
diff --git a/lcci/17.06.Number Of 2s In Range/README.md b/lcci/17.06.Number Of 2s In Range/README.md
index 84cde5282c08d..0c0e8c039313e 100644
--- a/lcci/17.06.Number Of 2s In Range/README.md
+++ b/lcci/17.06.Number Of 2s In Range/README.md
@@ -193,6 +193,45 @@ func numberOf2sInRange(n int) int {
}
```
+```swift
+class Solution {
+ private var a = [Int](repeating: 0, count: 12)
+ private var dp = [[Int]](repeating: [Int](repeating: -1, count: 12), count: 12)
+
+ func numberOf2sInRange(_ n: Int) -> Int {
+ var n = n
+ var len = 0
+ while n > 0 {
+ len += 1
+ a[len] = n % 10
+ n /= 10
+ }
+ for i in 0..<12 {
+ dp[i] = [Int](repeating: -1, count: 12)
+ }
+ return dfs(len, 0, true)
+ }
+
+ private func dfs(_ pos: Int, _ cnt: Int, _ limit: Bool) -> Int {
+ if pos <= 0 {
+ return cnt
+ }
+ if !limit && dp[pos][cnt] != -1 {
+ return dp[pos][cnt]
+ }
+ let up = limit ? a[pos] : 9
+ var ans = 0
+ for i in 0...up {
+ ans += dfs(pos - 1, cnt + (i == 2 ? 1 : 0), limit && i == up)
+ }
+ if !limit {
+ dp[pos][cnt] = ans
+ }
+ return ans
+ }
+}
+```
+
<!-- tabs:end -->
<!-- end -->
diff --git a/lcci/17.06.Number Of 2s In Range/README_EN.md b/lcci/17.06.Number Of 2s In Range/README_EN.md
index 8438234dc7a39..c64951884904a 100644
--- a/lcci/17.06.Number Of 2s In Range/README_EN.md
+++ b/lcci/17.06.Number Of 2s In Range/README_EN.md
@@ -196,6 +196,45 @@ func numberOf2sInRange(n int) int {
}
```
+```swift
+class Solution {
+ private var a = [Int](repeating: 0, count: 12)
+ private var dp = [[Int]](repeating: [Int](repeating: -1, count: 12), count: 12)
+
+ func numberOf2sInRange(_ n: Int) -> Int {
+ var n = n
+ var len = 0
+ while n > 0 {
+ len += 1
+ a[len] = n % 10
+ n /= 10
+ }
+ for i in 0..<12 {
+ dp[i] = [Int](repeating: -1, count: 12)
+ }
+ return dfs(len, 0, true)
+ }
+
+ private func dfs(_ pos: Int, _ cnt: Int, _ limit: Bool) -> Int {
+ if pos <= 0 {
+ return cnt
+ }
+ if !limit && dp[pos][cnt] != -1 {
+ return dp[pos][cnt]
+ }
+ let up = limit ? a[pos] : 9
+ var ans = 0
+ for i in 0...up {
+ ans += dfs(pos - 1, cnt + (i == 2 ? 1 : 0), limit && i == up)
+ }
+ if !limit {
+ dp[pos][cnt] = ans
+ }
+ return ans
+ }
+}
+```
+
<!-- tabs:end -->
<!-- end -->
diff --git a/lcci/17.06.Number Of 2s In Range/Solution.swift b/lcci/17.06.Number Of 2s In Range/Solution.swift
new file mode 100644
index 0000000000000..af7895395a1e5
--- /dev/null
+++ b/lcci/17.06.Number Of 2s In Range/Solution.swift
@@ -0,0 +1,36 @@
+class Solution {
+ private var a = [Int](repeating: 0, count: 12)
+ private var dp = [[Int]](repeating: [Int](repeating: -1, count: 12), count: 12)
+
+ func numberOf2sInRange(_ n: Int) -> Int {
+ var n = n
+ var len = 0
+ while n > 0 {
+ len += 1
+ a[len] = n % 10
+ n /= 10
+ }
+ for i in 0..<12 {
+ dp[i] = [Int](repeating: -1, count: 12)
+ }
+ return dfs(len, 0, true)
+ }
+
+ private func dfs(_ pos: Int, _ cnt: Int, _ limit: Bool) -> Int {
+ if pos <= 0 {
+ return cnt
+ }
+ if !limit && dp[pos][cnt] != -1 {
+ return dp[pos][cnt]
+ }
+ let up = limit ? a[pos] : 9
+ var ans = 0
+ for i in 0...up {
+ ans += dfs(pos - 1, cnt + (i == 2 ? 1 : 0), limit && i == up)
+ }
+ if !limit {
+ dp[pos][cnt] = ans
+ }
+ return ans
+ }
+}