Added elixir

Author: javadev

src/main/elixir/g0001_0100/s0001_two_sum/readme.md

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+[![](https://img.shields.io/github/stars/javadev/LeetCode-in-All?label=Stars&style=flat-square)](https://github.com/javadev/LeetCode-in-All)
+[![](https://img.shields.io/github/forks/javadev/LeetCode-in-All?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/javadev/LeetCode-in-All/fork)
+
+## 1\. Two Sum
+
+Easy
+
+Given an array of integers `nums` and an integer `target`, return _indices of the two numbers such that they add up to `target`_.
+
+You may assume that each input would have **_exactly_ one solution**, and you may not use the _same_ element twice.
+
+You can return the answer in any order.
+
+**Example 1:**
+
+**Input:** nums = [2,7,11,15], target = 9
+
+**Output:** [0,1]
+
+**Output:** Because nums[0] + nums[1] == 9, we return [0, 1]. 
+
+**Example 2:**
+
+**Input:** nums = [3,2,4], target = 6
+
+**Output:** [1,2] 
+
+**Example 3:**
+
+**Input:** nums = [3,3], target = 6
+
+**Output:** [0,1] 
+
+**Constraints:**
+
+*   <code>2 <= nums.length <= 10<sup>4</sup></code>
+*   <code>-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup></code>
+*   <code>-10<sup>9</sup> <= target <= 10<sup>9</sup></code>
+*   **Only one valid answer exists.**
+
+**Follow-up:** Can you come up with an algorithm that is less than <code>O(n<sup>2</sup>) </code>time complexity?
+
+## Solution
+
+```elixir
+defmodule Solution do
+  @spec two_sum(nums :: [integer], target :: integer) :: [integer]
+  def two_sum(nums, target) do
+    nums
+        |> Enum.with_index()
+        |> Enum.reduce_while(%{}, fn {num, index}, map ->
+            case map[target - num] do
+                nil -> {:cont, Map.put(map, num, index)}
+                found -> {:halt, [index, found]}
+            end
+        end)
+  end
+end
+```

src/main/elixir/g0001_0100/s0002_add_two_numbers/readme.md

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+[![](https://img.shields.io/github/stars/javadev/LeetCode-in-All?label=Stars&style=flat-square)](https://github.com/javadev/LeetCode-in-All)
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+
+## 2\. Add Two Numbers
+
+Medium
+
+You are given two **non-empty** linked lists representing two non-negative integers. The digits are stored in **reverse order**, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.
+
+You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2020/10/02/addtwonumber1.jpg)
+
+**Input:** l1 = [2,4,3], l2 = [5,6,4]
+
+**Output:** [7,0,8]
+
+**Explanation:** 342 + 465 = 807. 
+
+**Example 2:**
+
+**Input:** l1 = [0], l2 = [0]
+
+**Output:** [0] 
+
+**Example 3:**
+
+**Input:** l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
+
+**Output:** [8,9,9,9,0,0,0,1] 
+
+**Constraints:**
+
+*   The number of nodes in each linked list is in the range `[1, 100]`.
+*   `0 <= Node.val <= 9`
+*   It is guaranteed that the list represents a number that does not have leading zeros.
+
+## Solution
+
+```elixir
+# Definition for singly-linked list.
+#
+# defmodule ListNode do
+#   @type t :: %__MODULE__{
+#           val: integer,
+#           next: ListNode.t() | nil
+#         }
+#   defstruct val: 0, next: nil
+# end
+defmodule Solution do
+  @spec add_two_numbers(l1 :: ListNode.t | nil, l2 :: ListNode.t | nil) :: ListNode.t | nil
+  def add_two_numbers(l1, l2) do
+    add(l1, l2, 0)
+  end
+
+  defp add(nil, nil, 0), do: nil
+  defp add(l1, l2, carry) do
+    {val1, next1} = content(l1)
+    {val2, next2} = content(l2)
+    sum = val1 + val2 + carry
+    %ListNode{val: rem(sum, 10), next: add(next1, next2, div(sum, 10))}
+  end
+
+  defp content(nil), do: {0, nil}
+  defp content(node), do: {node.val, node.next}
+end
+```