Reverse integer.

Author: recherst

Easy/7.Reverse Integer.playground/Contents.swift

@@ -0,0 +1,49 @@
+/**
+ Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
+
+ Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
+
+  
+
+ Example 1:
+ Input: x = 123
+ Output: 321
+ 
+ Example 2:
+ Input: x = -123
+ Output: -321
+ 
+ Example 3:
+ Input: x = 120
+ Output: 21
+  
+
+ Constraints:
+ - -231 <= x <= 231 - 1
+ */
+class Solution {
+    func reverse(_ x: Int) -> Int {
+        let str = "\(abs(x))"
+        var i = str.count - 1
+        var res = ""
+        while i >= 0 {
+            let e = str[str.index(str.startIndex, offsetBy: i)]
+            res.append(e)
+            i -= 1
+        }
+        
+        if let res = Int(res) {
+            if x > 0 {
+                return res >= 2147483647 ? 0 : res
+            } else {
+                return -res <= -2147483648 ? 0 : -res
+            }
+        } else {
+            return 0
+        }
+    }
+}
+
+let s = Solution()
+let r = s.reverse(-2147483648)
+print(r)

Easy/7.Reverse Integer.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Easy/7.Reverse Integer.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -109,3 +109,5 @@
 2. [Longest Substring Without Repeating Characters](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/3.Longest%20Substring%20Without%20Repeating%20Characters.playground/Contents.swift)
 3. [Longest Palindromic Substring](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/5.Longest%20Palindromic%20Substring.playground/Contents.swift)
 4. [ZigZag Conversion](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/6.ZigZag%20Conversion.playground/Contents.swift)
+5. [Reverse Integer](https://github.com/recherst/leetcode-algtorithm/blob/main/Medium/7.Reverse%20Integer.playground/Contents.swift)
+