From 025638c3cc1291d1350edabc2e3c77a538e49010 Mon Sep 17 00:00:00 2001
From: sadcat <yezhi.zhang@gmail.com>
Date: Fri, 10 May 2019 10:55:09 +0800
Subject: [PATCH 1/2] week4 #1

---
 Week_04/id_113/leetcode_169.rb | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 Week_04/id_113/leetcode_169.rb

diff --git a/Week_04/id_113/leetcode_169.rb b/Week_04/id_113/leetcode_169.rb
new file mode 100644
index 00000000..272ea51b
--- /dev/null
+++ b/Week_04/id_113/leetcode_169.rb
@@ -0,0 +1,23 @@
+# @param {Integer[]} nums
+# @return {Integer}
+def majority_element(nums)
+  return nums[0] if nums.length == 1
+
+  counter = {}
+  z = 0
+  m = 0
+  nums.each do |n|
+    if counter.key?(n)
+      counter[n] += 1
+      if counter[n] > m
+        z = n
+        m = counter[n]
+      end
+      next
+    else
+      counter[n] = 1
+    end
+  end
+
+  z
+end

From d240b7ea2b88df165cc8857a74b16fd506754280 Mon Sep 17 00:00:00 2001
From: sadcat <yezhi.zhang@gmail.com>
Date: Sun, 12 May 2019 00:52:10 +0800
Subject: [PATCH 2/2] week4 #2

---
 Week_04/id_113/leetcode_742.rb | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 Week_04/id_113/leetcode_742.rb

diff --git a/Week_04/id_113/leetcode_742.rb b/Week_04/id_113/leetcode_742.rb
new file mode 100644
index 00000000..d72d6231
--- /dev/null
+++ b/Week_04/id_113/leetcode_742.rb
@@ -0,0 +1,20 @@
+# @param {Integer[]} cost
+# @return {Integer}
+def min_cost_climbing_stairs(cost)
+  m = []
+  dp(cost.length, cost, m)
+end
+
+def dp(n, cost, m)
+  return m[n] unless m[n].nil?
+  return 0 if n == -1
+  return cost[0] if n == 0
+
+  c = n == cost.length ? 0 : cost[n]
+  m[n] = c + min(dp(n - 1, cost, m), dp(n - 2, cost, m))
+  m[n]
+end
+
+def min(*values)
+  values.min
+end