diff --git a/300.LongestIncreasingSubsequence/binary_search.cpp b/300.LongestIncreasingSubsequence/binary_search.cpp
new file mode 100644
index 0000000..4f15f35
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/binary_search.cpp
@@ -0,0 +1,18 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    // least increasing order
+    vector<int> lis;
+
+    for (auto num : nums) {
+      auto it = lower_bound(lis.begin(), lis.end(), num);
+      if (it == lis.end()) {
+        lis.push_back(num);
+      } else {
+        *it = num;
+      }
+    }
+
+    return lis.size();
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/iteration_step1.cpp b/300.LongestIncreasingSubsequence/iteration_step1.cpp
new file mode 100644
index 0000000..1a2d55c
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/iteration_step1.cpp
@@ -0,0 +1,24 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    if (nums.empty()) {
+      return 0;
+    }
+    vector<int> increasing_nums;
+    increasing_nums.push_back(nums[0]);
+    for (int i = 1; i < nums.size(); i++) {
+      if (nums[i] > increasing_nums.back()) {
+        increasing_nums.push_back(nums[i]);
+        continue;
+      }
+      // find first larger or equal num
+      int greater_or_equal_index = 0;
+      while (nums[i] > increasing_nums[greater_or_equal_index]) {
+        greater_or_equal_index++;
+      }
+      increasing_nums[greater_or_equal_index] = nums[i];
+    }
+
+    return increasing_nums.size();
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/iteration_step2.cpp b/300.LongestIncreasingSubsequence/iteration_step2.cpp
new file mode 100644
index 0000000..53a4a2b
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/iteration_step2.cpp
@@ -0,0 +1,43 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    if (nums.empty()) {
+      return 0;
+    }
+    vector<int> increasing_nums;
+    increasing_nums.push_back(nums[0]);
+    for (int i = 1; i < nums.size(); i++) {
+      if (nums[i] > increasing_nums.back()) {
+        increasing_nums.push_back(nums[i]);
+        continue;
+      }
+      // find first larger or equal num
+      int index = FindFirstLargerOrEqualIndex(increasing_nums, nums[i]);
+      increasing_nums[index] = nums[i];
+    }
+
+    return increasing_nums.size();
+  }
+
+private:
+  int FindFirstLargerOrEqualIndex(vector<int>& nums, int target) {
+    int left = 0;
+    int right = nums.size();
+
+    while (left < right) {
+      int middle = left + (right - left) / 2;
+      if (nums[middle] < target) {
+        // middle の値がターゲットより小さい場合、
+        // ターゲットは middle の右側にある可能性がある。
+        // したがって、探索範囲を [middle + 1, right) に絞る
+        left = middle + 1;
+      } else {
+        // middle の値がターゲット以上の場合、
+        // middle は答えの候補であるか、ターゲットは middle の左側にある可能性がある。
+        // したがって、探索範囲を [left, middle) に絞る。
+        right = middle;
+      }
+    }
+    return left;
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/memo.md b/300.LongestIncreasingSubsequence/memo.md
new file mode 100644
index 0000000..55f1de0
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/memo.md
@@ -0,0 +1,52 @@
+## ステップ1
+思いついたのは愚直にループを回しながら頭からみていく方法と
+頭から1歩ずつ進んでいき、地点ごとの最大距離をメモ化する
+
+メモ化のロジックを、形で覚えてしまっている感がある
+15分ほどでaccept
+
+時間計算量
+O(n^2)
+
+空間計算量
+O(n)
+
+## ステップ2
+・メモ化のvectorの名前をmemoizationから変更
+
+## 他の解法
+binary_searchでも解くことができる
+https://github.com/Yoshiki-Iwasa/Arai60/pull/46/commits/56e8cf4d4efc42c5784108191d1e5fc615de9206
+
+こちらも二分探索
+他にもBitとセグメント木というものがある(名前を聞いたことがあるようなないような。。。)
+ぱっと見「アルゴリズムイントロダクション」に載っていない？
+https://github.com/fhiyo/leetcode/pull/32/commits/4ddb934198ff85e6349b064edea5fe312bd27b9c
+
+基本方針はみなさんメモ化かな、二分探索もできた方がいいか
+https://github.com/SuperHotDogCat/coding-interview/pull/28/commits/b81e3d1929c84abea2f00ef3b20b5a34b79eec38
+https://github.com/sakupan102/arai60-practice/pull/32
+
+マジックナンバーについて
+> 入力の制約を守らない入力を入れると、理解できない振る舞いをするんですよね。
+> 数年間使うコードならば、そういうことは間違いなく起きますよね。
+制約値よりは、std::numeric_limits::min()とstd::numeric_limits::max()を使うか
+https://github.com/Exzrgs/LeetCode/pull/18
+
+## 二分探索
+binary_search.cppに実装
+numsの中の最小値に出会うたびに先頭から入れ替えが走る
+入れ替え後から大きな数が現れると要素が後ろに追加される
+
+https://en.cppreference.com/w/cpp/algorithm/lower_bound
+時間計算量
+O(n log n)
+要素数がnでそのループ内のlower_boundがlog n
+
+空間計算量
+O(n)
+
+メモ：下記のケースを使うと理解しやすい
+{10, 9, 2, 5, 3, 7, 101, 18, 1, 2, 3, 4, 5, 6, 7, 8}
+
+
diff --git a/300.LongestIncreasingSubsequence/step1.cpp b/300.LongestIncreasingSubsequence/step1.cpp
new file mode 100644
index 0000000..ae41198
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/step1.cpp
@@ -0,0 +1,18 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    vector<int> memoization(nums.size(), 1);
+
+    int max_length = 0;
+    for (int i = 0; i < nums.size(); i++) {
+      for (int j = 0; j < i; j++) {
+        if (nums[i] > nums[j]) {
+          memoization[i] = max(memoization[i], memoization[j] + 1);
+        }
+      }
+      max_length = max(max_length, memoization[i]);
+    }
+
+    return max_length;
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/step2.cpp b/300.LongestIncreasingSubsequence/step2.cpp
new file mode 100644
index 0000000..ace8598
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/step2.cpp
@@ -0,0 +1,18 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    vector<int> longest_lengths(nums.size(), 1);
+
+    int max_length = 0;
+    for (int i = 0; i < nums.size(); i++) {
+      for (int j = 0; j < i; j++) {
+        if (nums[i] > nums[j]) {
+          longest_lengths[i] = max(longest_lengths[i], longest_lengths[j] + 1);
+        }
+      }
+      max_length = max(max_length, longest_lengths[i]);
+    }
+
+    return max_length;
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/step3.cpp b/300.LongestIncreasingSubsequence/step3.cpp
new file mode 100644
index 0000000..2fe6d03
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/step3.cpp
@@ -0,0 +1,19 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    vector<int> longest_lengths(nums.size(), 1);
+
+    int max_length = 0;
+    for (int i = 0; i < nums.size(); i++) {
+      for (int j = 0; j < i; j++) {
+        if (nums[i] > nums[j]) {
+          longest_lengths[i] = max(longest_lengths[i], longest_lengths[j] + 1);
+        }
+      }
+
+      max_length = max(max_length, longest_lengths[i]);
+    }
+
+    return max_length;
+  }
+};
diff --git a/300.LongestIncreasingSubsequence/step4.cpp b/300.LongestIncreasingSubsequence/step4.cpp
new file mode 100644
index 0000000..d1494b1
--- /dev/null
+++ b/300.LongestIncreasingSubsequence/step4.cpp
@@ -0,0 +1,19 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    vector<int> longest_lengths(nums.size(), 1);
+
+    int max_length = 0;
+    for (int i = 0; i < nums.size(); i++) {
+      for (int j = 0; j < i; j++) {
+        if (nums[j] < nums[i]) {
+          longest_lengths[i] = max(longest_lengths[i], longest_lengths[j] + 1);
+        }
+      }
+
+      max_length = max(max_length, longest_lengths[i]);
+    }
+
+    return max_length;
+  }
+};
diff --git a/problem_name/step1.cpp b/problem_name/step1.cpp
index e69de29..1a2d55c 100644
--- a/problem_name/step1.cpp
+++ b/problem_name/step1.cpp
@@ -0,0 +1,24 @@
+class Solution {
+public:
+  int lengthOfLIS(vector<int>& nums) {
+    if (nums.empty()) {
+      return 0;
+    }
+    vector<int> increasing_nums;
+    increasing_nums.push_back(nums[0]);
+    for (int i = 1; i < nums.size(); i++) {
+      if (nums[i] > increasing_nums.back()) {
+        increasing_nums.push_back(nums[i]);
+        continue;
+      }
+      // find first larger or equal num
+      int greater_or_equal_index = 0;
+      while (nums[i] > increasing_nums[greater_or_equal_index]) {
+        greater_or_equal_index++;
+      }
+      increasing_nums[greater_or_equal_index] = nums[i];
+    }
+
+    return increasing_nums.size();
+  }
+};