Create binary-search.py

Author: kamyu104

Python/binary-search.py

@@ -0,0 +1,42 @@
+# Time:  O(logn)
+# Space: O(1)
+
+# Given a sorted (in ascending order) integer array nums of n elements
+# and a target value, write a function to search target in nums.
+# If target exists, then return its index, otherwise return -1.
+#
+# Example 1:
+#
+# Input: nums = [-1,0,3,5,9,12], target = 9
+# Output: 4
+# Explanation: 9 exists in nums and its index is 4
+#
+# Example 2:
+#
+# Input: nums = [-1,0,3,5,9,12], target = 2
+# Output: -1
+# Explanation: 2 does not exist in nums so return -1
+#
+# Note:
+# - You may assume that all elements in nums are unique.
+# - n will be in the range [1, 10000].
+# - The value of each element in nums will be in the range [-9999, 9999].
+
+
+class Solution(object):
+    def search(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: int
+        """
+        left, right = 0, len(nums)-1
+        while left <= right:
+            mid = left + (right-left)//2
+            if nums[mid] > target:
+                right = mid-1
+            elif nums[mid] < target:
+                left = mid+1
+            else:
+                return mid
+        return -1