binary search 1

rotated-sorted-array.py

@@ -0,0 +1,30 @@
+# time: O(logn)
+# space: O(1)
+
+class Solution:
+    def search(self, nums: List[int], target: int) -> int:
+        left = 0
+        right = len(nums)-1
+
+        # [6,0,1,2,3]
+         # l   m   r    
+        # [4,5,6,7,0,1,2] 6
+        #  l     m     r
+        while left <= right:
+            mid = left + (right - left)//2
+
+            if nums[mid] == target:
+                return mid
+
+            if nums[left] <= nums[mid]:
+                if nums[left] <= target < nums[mid]:
+                    right = mid - 1
+                else:
+                    left = mid + 1
+            else:
+                if nums[mid] < target <= nums[right]:
+                    left = mid + 1
+                else:
+                    right = mid - 1
+
+        return -1 

search-2d-matrix.py

@@ -0,0 +1,32 @@
+class Solution:
+    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
+        cols = len(matrix[0])
+        rows = len(matrix)
+
+        top = 0
+        bot = rows - 1
+        found = False
+        while top <= bot:
+            row = top + (bot - top)//2
+            if matrix[row][0] > target:
+                bot = row - 1
+            elif matrix[row][-1] < target:
+                top = row + 1
+            else:
+                found = True
+                break
+
+        if not found:
+            return False
+        left = 0
+        right = len(matrix[0])-1
+        while left <= right:
+            mid = left + (right - left)//2
+            if matrix[row][mid] == target:
+                return True
+            if matrix[row][mid] < target:
+                left = mid + 1
+            else:
+                right = mid - 1
+
+        return False

sorted-array-unknown-size.py

@@ -0,0 +1,23 @@
+
+
+class Solution:
+    def search(self, reader: 'ArrayReader', target: int) -> int:
+
+        left = 0
+        right = 1
+
+        # O(logn)
+        while reader.get(i) < target:
+            left = right
+            right = right * 2
+        # O(logn)
+        while left <= right:
+            mid = left + (right-left)//2
+            if reader.get(mid)==target:
+                return mid
+            elif reader.get(mid) < target: 
+                left = mid + 1
+            else:
+                right = mid - 1
+
+        return -1