feat: [Week 10-2] solve search in rotated sorted array

Author: Chaedie

search-in-rotated-sorted-array/Chaedie.py

@@ -0,0 +1,77 @@
+"""
+1) binary search 로 pivot 찾아 2번 binary search 하기
+Time: O(log(n))
+Space: O(1)
+"""
+
+
+class Solution:
+    def search(self, nums: List[int], target: int) -> int:
+
+        def find_pivot():
+            low, high = 0, len(nums) - 1
+            while low <= high:
+                mid = (low + high) // 2
+                if mid > 0 and nums[mid - 1] >= nums[mid]:
+                    return mid
+                if nums[0] <= nums[mid]:
+                    low = mid + 1
+                else:
+                    high = mid - 1
+            return 0
+
+        def binary_search(low, high):
+            while low <= high:
+                mid = (low + high) // 2
+                if nums[mid] == target:
+                    return mid
+                if nums[mid] < target:
+                    low = mid + 1
+                else:
+                    high = mid - 1
+            return -1
+
+        pivot = find_pivot()
+
+        idx = binary_search(0, pivot - 1)
+        return idx if idx > -1 else binary_search(pivot, len(nums) - 1)
+
+
+"""
+2) binary search
+    left sorted case
+    4 5 6 7 0 1 2 3
+        m
+        left target case
+        right target case
+
+    right sorted case
+    6 7 0 1 2 3 4 5
+            m
+        left target case
+        right target case
+Time: O(log(n))
+Space: O(1)
+"""
+
+
+class Solution:
+    def search(self, nums: List[int], target: int) -> int:
+
+        low, high = 0, len(nums) - 1
+        while low <= high:
+            mid = (low + high) // 2
+            if target == nums[mid]:
+                return mid
+
+            if nums[low] <= nums[mid]:
+                if nums[low] <= target <= nums[mid]:
+                    high = mid - 1
+                else:
+                    low = mid + 1
+            else:
+                if nums[mid] <= target <= nums[high]:
+                    low = mid + 1
+                else:
+                    high = mid - 1
+        return -1