diff --git a/study-plan/algorithm/day-1/binary-search.rb b/study-plan/algorithm/day-1/binary-search.rb
new file mode 100644
index 0000000..37103ef
--- /dev/null
+++ b/study-plan/algorithm/day-1/binary-search.rb
@@ -0,0 +1,31 @@
+# @param {Integer[]} nums
+# @param {Integer} target
+# @return {Integer}
+def search(nums, target)
+    left = 0
+    right = nums.size
+
+    while left < right do
+        mid = (left + right).div(2)
+
+        if nums[mid] == target then
+            return mid
+        elsif nums[mid] < target then
+            left = mid + 1
+        else
+            right = mid
+        end
+    end
+
+    return -1
+end
+
+RSpec.describe "search" do
+    it "nums = [-1,0,3,5,9,12], target = 9" do
+        expect(search([-1,0,3,5,9,12], 9)).to eq(4)
+    end
+
+    it "nums = [-1,0,3,5,9,12], target = 2" do
+        expect(search([-1,0,3,5,9,12], 2)).to eq(-1)
+    end
+end
diff --git a/study-plan/algorithm/day-1/first-bad-version.rb b/study-plan/algorithm/day-1/first-bad-version.rb
new file mode 100644
index 0000000..60c33cf
--- /dev/null
+++ b/study-plan/algorithm/day-1/first-bad-version.rb
@@ -0,0 +1,46 @@
+# The is_bad_version API is already defined for you.
+# @param {Integer} version
+# @return {boolean} whether the version is bad
+# def is_bad_version(version):
+
+# @param {Integer} n
+# @return {Integer}
+def first_bad_version(n)
+    left = 1
+    right = n
+
+    while left < right do
+        mid = (left + right).div(2)
+
+        if is_bad_version(mid) then
+            right = mid
+        else
+            left = mid + 1
+        end
+    end
+
+    return left
+end
+
+RSpec.describe "first_bad_version" do
+    it "n = 5, bad = 4" do
+        def is_bad_version(n)
+            return n >= 4
+        end
+        expect(first_bad_version(5)).to eq(4)
+    end
+
+    it "n = 1, bad = 1" do
+        def is_bad_version(n)
+            return n >= 1
+        end
+        expect(first_bad_version(1)).to eq(1)
+    end
+
+    it "n = 1000000, bad = 76192" do
+        def is_bad_version(n)
+            return n >= 76192
+        end
+        expect(first_bad_version(1000000)).to eq(76192)
+    end
+end
diff --git a/study-plan/algorithm/day-1/search-insert-position.rb b/study-plan/algorithm/day-1/search-insert-position.rb
new file mode 100644
index 0000000..b2c2bf7
--- /dev/null
+++ b/study-plan/algorithm/day-1/search-insert-position.rb
@@ -0,0 +1,35 @@
+# @param {Integer[]} nums
+# @param {Integer} target
+# @return {Integer}
+def search_insert(nums, target)
+    left = 0
+    right = nums.size
+
+    while left < right do
+        mid = (left + right).div(2)
+
+        if nums[mid] == target then
+            return mid
+        elsif nums[mid] < target then
+            left = mid + 1
+        else
+            right = mid
+        end
+    end
+
+    return left
+end
+
+RSpec.describe "search_insert" do
+    it "nums = [1,3,5,6], target = 5" do
+        expect(search_insert([1,3,5,6], 5)).to eq(2)
+    end
+
+    it "nums = [1,3,5,6], target = 2" do
+        expect(search_insert([1,3,5,6], 2)).to eq(1)
+    end
+
+    it "nums = [1,3,5,6], target = 7" do
+        expect(search_insert([1,3,5,6], 7)).to eq(4)
+    end
+end