Add Two Numbers

Author: ShawnFoo

Swift/Add_Two_Numbers.playground/Contents.swift

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+/*
+ Add Two Numbers
+ 
+ Tag: Linked List、 Math
+ 
+ https://leetcode.com/problems/add-two-numbers/description/
+ */
+
+public class ListNode {
+    public var val: Int
+    public var next: ListNode?
+    
+    public init(_ val: Int) {
+        self.val = val
+        self.next = nil
+    }
+}
+
+/**
+ 思路: 按位加, 处理好满10进1位即可
+ */
+class Solution {
+    func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        var listHead: ListNode?
+        var addOneNext = false // 下一位进1
+        var listLastNode: ListNode?
+        var n1: ListNode? = l1
+        var n2: ListNode? = l2
+        while n1 != nil || n2 != nil {
+            let d1 = n1 != nil ? n1!.val : 0
+            let d2 = n2 != nil ? n2!.val : 0
+            var digitSum = d1 + d2 + (addOneNext ? 1 : 0) // 对应位置两数相加, 以及进位1
+            if n1 != nil {
+                n1 = n1!.next
+            }
+            if n2 != nil {
+                n2 = n2!.next
+            }
+            addOneNext = digitSum >= 10 // 两数相加大于10, 标记下一位进1
+            digitSum %= 10
+            if let lastNode = listLastNode {
+                lastNode.next = ListNode(digitSum)
+                listLastNode = lastNode.next
+            }
+            else { // 头节点
+                listHead = ListNode(digitSum)
+                listLastNode = listHead
+            }
+        }
+        if (addOneNext) { // 相同长度的两个单向链表 最后位置节点 满10进1
+            listLastNode!.next = ListNode(1)
+        }
+        return listHead
+    }
+}
+
+

Swift/Add_Two_Numbers.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>