Algorithm

lc 704: Binary Search

Program description
Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
You must write an algorithm with O(log n) runtime complexity.

Example 1:
Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Constraints:
1 <= nums.length <= 104
-104 < nums[i], target < 104
All the integers in nums are unique.
nums is sorted in ascending order.

Solution 1: left close, right close

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        left = 0
        right = len(nums)-1
        while left <= right:
            mid = (left+right) // 2
            if target < nums[mid]:
                right = mid-1
            elif target > nums[mid]:
                left = mid+1
            else:
                return mid
        return -1

Solution 1: left close, right open

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        left = 0
        right = len(nums)
        while left < right:
            mid = (left+right) // 2
            if target < nums[mid]:
                right = mid
            elif target > nums[mid]:
                left = mid + 1
            else:
                return mid
        return -1

lc 27: Remove Element

Problem description

solution:

class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        slow = 0
        fast = 0
        while fast < len(nums):
            if nums[fast] != val:
                nums[slow] = nums[fast]
                slow += 1
            fast += 1
        return slow