Add string.

Author: recherst

Easy/415.Add Strings.playground/Contents.swift

@@ -0,0 +1,69 @@
+/**
+ Given two non-negative integers, num1 and num2 represented as string, return the sum of num1 and num2 as a string.
+
+ You must solve the problem without using any built-in library for handling large integers (such as BigInteger). You must also not convert the inputs to integers directly.
+
+  
+
+ Example 1:
+ Input: num1 = "11", num2 = "123"
+ Output: "134"
+ 
+ Example 2:
+ Input: num1 = "456", num2 = "77"
+ Output: "533"
+ 
+ Example 3:
+ Input: num1 = "0", num2 = "0"
+ Output: "0"
+  
+
+ Constraints:
+ - 1 <= num1.length, num2.length <= 104
+ - num1 and num2 consist of only digits.
+ - num1 and num2 don't have any leading zeros except for the zero itself.
+ */
+class Solution {
+    func addStrings(_ num1: String, _ num2: String) -> String {
+        let sample: [Character: Int] = ["0": 0, "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8, "9": 9]
+        var num1Arr: [Character] = num1.map { $0 }.reversed()
+        var num2Arr: [Character] = num2.map { $0 }.reversed()
+        var carryCount = 0
+        var result = ""
+        if num1Arr.count < num2Arr.count {
+            let temp = num1Arr
+            num1Arr = num2Arr
+            num2Arr = temp
+        }
+        
+        for (i, c) in num1Arr.enumerated() {
+            let n1 = sample[c]!
+            var number = 0
+            if i <= num2Arr.count - 1 {
+                let n2 = sample[num2Arr[i]]!
+                number = n1 + n2
+            } else {
+                number = n1
+            }
+            if i > 0 && i == carryCount {
+                number += 1
+            }
+            if number >= 10 {
+                result.append("\(number)".last!)
+                carryCount = i + 1
+            } else {
+                result.append("\(number)")
+            }
+        }
+        if carryCount == num1Arr.count {
+            result.append("1")
+        }
+        
+        let arr: [String] = result.map { String($0) }.reversed()
+        return arr.joined()
+    }
+}
+
+let s = Solution()
+let r = s.addStrings("52", "60")
+print(r)

Easy/415.Add Strings.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/415.Add Strings.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -86,6 +86,7 @@
 82. [Longest Palindrome](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/409.Longest%20Palindrome.playground/Contents.swift)
 83. [Fizz Buzz](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/409.Fizz%20Buzz.playground/Contents.swift)
 84. [Third Maximum Number](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/414.Third%20Maximum%20Number.playground/Contents.swift)
+85. [Add String](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/415.Add%20String.playground/Contents.swift)
 
 #### Medium