From 0bfc4c7cea129d206334c3191b2c761458825efa Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Mon, 13 May 2024 08:07:40 +0100
Subject: [PATCH 1/3] Swift Implementation for LCCI 17.21

---
 lcci/17.21.Volume of Histogram/Solution.swift | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 lcci/17.21.Volume of Histogram/Solution.swift

diff --git a/lcci/17.21.Volume of Histogram/Solution.swift b/lcci/17.21.Volume of Histogram/Solution.swift
new file mode 100644
index 0000000000000..61d30a3e741d4
--- /dev/null
+++ b/lcci/17.21.Volume of Histogram/Solution.swift	
@@ -0,0 +1,29 @@
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        let n = height.count
+        if n < 3 {
+            return 0
+        }
+        
+        var left = [Int](repeating: 0, count: n)
+        var right = [Int](repeating: 0, count: n)
+        
+        left[0] = height[0]
+        right[n - 1] = height[n - 1]
+
+        for i in 1..<n {
+            left[i] = max(left[i - 1], height[i])
+        }
+
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            right[i] = max(right[i + 1], height[i])
+        }
+
+        var ans = 0
+        for i in 0..<n {
+            ans += min(left[i], right[i]) - height[i]
+        }
+        
+        return ans
+    }
+}
\ No newline at end of file

From 531ea2d78b47741908cd60aa054af18481810e26 Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Mon, 13 May 2024 08:08:19 +0100
Subject: [PATCH 2/3] Swift Implementation for LCCI 17.21

---
 lcci/17.21.Volume of Histogram/README.md    | 32 +++++++++++++++++++++
 lcci/17.21.Volume of Histogram/README_EN.md | 32 +++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/lcci/17.21.Volume of Histogram/README.md b/lcci/17.21.Volume of Histogram/README.md
index f7efe350feec0..ec507a732b72d 100644
--- a/lcci/17.21.Volume of Histogram/README.md	
+++ b/lcci/17.21.Volume of Histogram/README.md	
@@ -156,6 +156,38 @@ public class Solution {
 }
 ```
 
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        let n = height.count
+        if n < 3 {
+            return 0
+        }
+        
+        var left = [Int](repeating: 0, count: n)
+        var right = [Int](repeating: 0, count: n)
+        
+        left[0] = height[0]
+        right[n - 1] = height[n - 1]
+
+        for i in 1..<n {
+            left[i] = max(left[i - 1], height[i])
+        }
+
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            right[i] = max(right[i + 1], height[i])
+        }
+
+        var ans = 0
+        for i in 0..<n {
+            ans += min(left[i], right[i]) - height[i]
+        }
+        
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->
diff --git a/lcci/17.21.Volume of Histogram/README_EN.md b/lcci/17.21.Volume of Histogram/README_EN.md
index c934f608d3a0d..8541de815a9ad 100644
--- a/lcci/17.21.Volume of Histogram/README_EN.md	
+++ b/lcci/17.21.Volume of Histogram/README_EN.md	
@@ -150,6 +150,38 @@ public class Solution {
 }
 ```
 
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        let n = height.count
+        if n < 3 {
+            return 0
+        }
+        
+        var left = [Int](repeating: 0, count: n)
+        var right = [Int](repeating: 0, count: n)
+        
+        left[0] = height[0]
+        right[n - 1] = height[n - 1]
+
+        for i in 1..<n {
+            left[i] = max(left[i - 1], height[i])
+        }
+
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            right[i] = max(right[i + 1], height[i])
+        }
+
+        var ans = 0
+        for i in 0..<n {
+            ans += min(left[i], right[i]) - height[i]
+        }
+        
+        return ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

From 4cfd41262a91cd276c8402188598a9296118a52a Mon Sep 17 00:00:00 2001
From: klever34 <klever34@users.noreply.github.com>
Date: Mon, 13 May 2024 07:09:37 +0000
Subject: [PATCH 3/3] style: format code and docs with prettier

---
 lcci/17.21.Volume of Histogram/README.md    | 6 +++---
 lcci/17.21.Volume of Histogram/README_EN.md | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/lcci/17.21.Volume of Histogram/README.md b/lcci/17.21.Volume of Histogram/README.md
index ec507a732b72d..7b4ffd2cfe962 100644
--- a/lcci/17.21.Volume of Histogram/README.md	
+++ b/lcci/17.21.Volume of Histogram/README.md	
@@ -163,10 +163,10 @@ class Solution {
         if n < 3 {
             return 0
         }
-        
+
         var left = [Int](repeating: 0, count: n)
         var right = [Int](repeating: 0, count: n)
-        
+
         left[0] = height[0]
         right[n - 1] = height[n - 1]
 
@@ -182,7 +182,7 @@ class Solution {
         for i in 0..<n {
             ans += min(left[i], right[i]) - height[i]
         }
-        
+
         return ans
     }
 }
diff --git a/lcci/17.21.Volume of Histogram/README_EN.md b/lcci/17.21.Volume of Histogram/README_EN.md
index 8541de815a9ad..a0557cd372146 100644
--- a/lcci/17.21.Volume of Histogram/README_EN.md	
+++ b/lcci/17.21.Volume of Histogram/README_EN.md	
@@ -157,10 +157,10 @@ class Solution {
         if n < 3 {
             return 0
         }
-        
+
         var left = [Int](repeating: 0, count: n)
         var right = [Int](repeating: 0, count: n)
-        
+
         left[0] = height[0]
         right[n - 1] = height[n - 1]
 
@@ -176,7 +176,7 @@ class Solution {
         for i in 0..<n {
             ans += min(left[i], right[i]) - height[i]
         }
-        
+
         return ans
     }
 }