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diff --git a/35-search-insert-position/problem.md b/35-search-insert-position/problem.md
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+## 問題: [35. Search Insert Position](https://leetcode.com/problems/search-insert-position/description/)
diff --git a/35-search-insert-position/step1.md b/35-search-insert-position/step1.md
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+# Step 1
+
+- 二分探索で解く
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        start_index, end_index = 0, len(nums) - 1
+        while start_index <= end_index:
+            middle_index = (start_index + end_index) // 2
+            if nums[middle_index] == target:
+                return middle_index
+            elif nums[middle_index] < target:
+                start_index = middle_index + 1
+            else:
+                end_index = middle_index - 1
+        return start_index
+```
+
+時間計算量: $O(\log n)$
+
+空間計算量: $O(1)$
diff --git a/35-search-insert-position/step2.md b/35-search-insert-position/step2.md
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+# Step 2
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        start, end = 0, len(nums) - 1
+        while start <= end:
+            middle = start + (end - start) // 2
+            if nums[middle] == target:
+                return middle
+            elif nums[middle] < target:
+                start = middle + 1
+            else:
+                end = middle - 1
+        return start
+```
diff --git a/35-search-insert-position/step3.md b/35-search-insert-position/step3.md
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+# Step 3
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        start, end = 0, len(nums) - 1
+        while start <= end:
+            middle = start + (end - start) // 2
+            if nums[middle] == target:
+                return middle
+            elif nums[middle] > target:
+                end = middle - 1
+            else:
+                start = middle + 1
+        return start
+```
+
+1回目: 1分　31秒
+
+2回目: 1分　26秒
+
+3回目: 1分　27秒