Completed Binary Search 1

Problem1.py

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+## Problem1 
+# Search a 2D Matrix (https://leetcode.com/problems/search-a-2d-matrix/)
+class Solution:
+    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
+        rows = len(matrix)
+        cols = len(matrix[0])
+
+        low = 0
+        high = (rows * cols) - 1
+
+        # treat the matrix as 1D array
+        while low <= high:
+            mid = low + (high - low) // 2
+            # convert 1D mid to row and column index of the matrix
+            # they are functions of the number of columns
+            row = mid // cols
+            col = mid % cols
+
+            valueAtMid = matrix[row][col]
+            if valueAtMid == target:
+                return True
+
+            if target < valueAtMid:
+                high = mid - 1
+            else:
+                low = mid + 1
+
+        return False

Problem2.py

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+## Problem2
+# Search in a Rotated Sorted Array (https://leetcode.com/problems/search-in-rotated-sorted-array/description/)
+
+class Solution:
+    def search(self, nums: List[int], target: int) -> int:
+        low = 0
+        high = len(nums) - 1
+
+        while low < high:
+            mid = low + (high - low) // 2
+            if nums[mid] == target:
+                return mid
+
+            # check which part is sorted
+            # left sorted
+            if nums[low] <= nums[mid]:
+                # if target is within the left sorted part
+                # bring high to mid - 1 and run binary search on it
+                if nums[low] <= target and target < nums[mid]:
+                    high = mid - 1
+                else: # else seaerch on right
+                    low = mid + 1
+            # right sorted
+            else:
+                # if target is within the right sorted part
+                # bring low to mid + 1 and run binary search on it
+                if nums[mid] < target and target <= nums[high]:
+                    low = mid + 1
+                else: # else search on left
+                    high = mid - 1
+        return low if nums[low] == target else -1

Problem3.py

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+## Problem3
+# Search in Infinite sorted array (https://leetcode.com/problems/search-in-a-sorted-array-of-unknown-size/description/)
+# """
+# This is ArrayReader's API interface.
+# You should not implement it, or speculate about its implementation
+# """
+# class ArrayReader:
+#     def get(self, index: int) -> int:
+
+class ArrayReader:
+    def __init__(self, arr: list[int]):
+        self.arr = arr
+
+    def get(self, index: int) -> int:
+        if index < len(self.arr):
+            return self.arr[index]
+        return 2**31 - 1
+
+class Solution:
+    def search(self, reader: "ArrayReader", target: int) -> int:
+        # Phase 1: find the low and high range
+        low = 0
+        high = 1
+
+        # we will keep moving the right pointer by 2x until we reach an index > target index
+        while reader.get(high) < target:
+            low = high
+            high = high * 2
+
+        # Phase 2: Binary search
+        while low <= high:
+            mid = low + (high - low) // 2
+            midVal = reader.get(mid)
+            if midVal == target:
+                return mid
+
+            if midVal > target:
+                high = mid - 1
+            else:
+                low = mid + 1
+
+        return -1
+
+
+# --- Execution Example ---
+if __name__ == "__main__":
+    # Define your sorted array here
+    my_array = [-1, 0, 3, 5, 9, 12, 15, 18, 22, 45, 67, 89]
+    target_value = 9
+
+    # Instantiate the mock reader with your array
+    reader = ArrayReader(my_array)
+
+    # Run the solution
+    sol = Solution()
+    result = sol.search(reader, target_value)
+
+    print(f"Target {target_value} found at index: {result}")