From f0dd82e39d398c2203ba708d39656d220072b49c Mon Sep 17 00:00:00 2001
From: Manuel Pineda <manuelpineda@google.com>
Date: Mon, 18 Jan 2021 14:04:52 +0100
Subject: [PATCH] [LeetCode] Add January 18.

---
 solved/LeetCode/Challenges/2020/January/18.kt | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 solved/LeetCode/Challenges/2020/January/18.kt

diff --git a/solved/LeetCode/Challenges/2020/January/18.kt b/solved/LeetCode/Challenges/2020/January/18.kt
new file mode 100644
index 00000000..c0ca9630
--- /dev/null
+++ b/solved/LeetCode/Challenges/2020/January/18.kt
@@ -0,0 +1,16 @@
+class Solution {
+  fun maxOperations(nums: IntArray, k: Int): Int {
+    val freq = mutableMapOf<Int, Int>()
+    var ans = 0
+    for (i in nums) {
+      val target = k - i
+      if ((freq[target] ?: 0) > 0) {
+        freq.put(target, freq[target]!! -1)
+        ans++
+      } else {
+        freq[i] = (freq[i] ?: 0) + 1 
+      }
+    }
+    return ans
+  }
+}