algorithm(i): add day 2 and rename day 1

Signed-off-by: Matej Focko <mfocko@redhat.com>

study-plan/algorithm/day-02/rotate-array.rb

@@ -0,0 +1,68 @@
+# @param {Integer[]} nums
+# @param {Integer} k
+# @return {Void} Do not return anything, modify nums in-place instead.
+def rotate(nums, k)
+    def reverse(nums, from, to)
+        while from < to do
+            nums[from], nums[to] = nums[to], nums[from]
+
+            from += 1
+            to -= 1
+        end
+    end
+
+    k = k % nums.size
+    reverse(nums, 0, nums.size - 1)
+    reverse(nums, 0, k - 1)
+    reverse(nums, k, nums.size - 1)
+end
+
+RSpec.describe "rotate" do
+    it "nums = [1,2,3,4,5,6,7], k = 0" do
+        nums = [1,2,3,4,5,6,7]
+        k = 0
+
+        rotate(nums, k)
+        expect(nums).to eq([1,2,3,4,5,6,7])
+    end
+
+    it "nums = [1,2,3,4,5,6,7], k = 1" do
+        nums = [1,2,3,4,5,6,7]
+        k = 1
+
+        rotate(nums, k)
+        expect(nums).to eq([7,1,2,3,4,5,6])
+    end
+
+    it "nums = [1,2,3,4,5,6,7], k = 2" do
+        nums = [1,2,3,4,5,6,7]
+        k = 2
+
+        rotate(nums, k)
+        expect(nums).to eq([6,7,1,2,3,4,5])
+    end
+
+    it "nums = [1,2,3,4,5,6,7], k = 3" do
+        nums = [1,2,3,4,5,6,7]
+        k = 3
+
+        rotate(nums, k)
+        expect(nums).to eq([5,6,7,1,2,3,4])
+    end
+
+    it "nums = [-1,-100,3,99], k = 1" do
+        nums = [-1,-100,3,99]
+        k = 1
+
+        rotate(nums, k)
+        expect(nums).to eq([99,-1,-100,3])
+    end
+
+    it "nums = [-1,-100,3,99], k = 2" do
+        nums = [-1,-100,3,99]
+        k = 2
+
+        rotate(nums, k)
+        expect(nums).to eq([3,99,-1,-100])
+    end
+end

study-plan/algorithm/day-02/squares-of-a-sorted-array.rb

@@ -0,0 +1,57 @@
+# @param {Integer[]} nums
+# @return {Integer[]}
+def sorted_squares(nums)
+    result = []
+
+    split = nums.find_index { |x| x >= 0 }
+
+    i, j = nil, nil
+    if split == nil then
+        i, j = nums.size - 1, nums.size
+    else
+        i, j = split - 1, split
+    end
+
+    while i >= 0 and j < nums.size do
+        i_s = nums[i] * nums[i]
+        j_s = nums[j] * nums[j]
+
+        if i_s < j_s then
+            result.push(i_s)
+            i -= 1
+        else
+            result.push(j_s)
+            j += 1
+        end
+    end
+
+    while i >= 0 do
+        result.push(nums[i] * nums[i])
+        i -= 1
+    end
+
+    while j < nums.size do
+        result.push(nums[j] * nums[j])
+        j += 1
+    end
+
+    return result
+end
+
+RSpec.describe "rotate" do
+    it "nums = [-4,-1,0,3,10]" do
+        expect(sorted_squares([-4,-1,0,3,10])).to eq([0,1,9,16,100])
+    end
+
+    it "nums = [-7,-3,2,3,11]" do
+        expect(sorted_squares([-7,-3,2,3,11])).to eq([4,9,9,49,121])
+    end
+
+    it "nums = [-7,-3,0,0,0,0,2,3,11]" do
+        expect(sorted_squares([-7,-3,0,0,0,0,2,3,11])).to eq([0,0,0,0,4,9,9,49,121])
+    end
+
+    it "nums = [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]" do
+        expect(sorted_squares([1,1,1,1,1,1,1,1,1,1,1,1,1,1,1])).to eq([1,1,1,1,1,1,1,1,1,1,1,1,1,1,1])
+    end
+end