167._Two_Sum_II_-_Input_Array_.py

"""Problem No.: 167
Problem:  Two Sum II - Input Array Is Sorted
DS:  Hash map
Approach:
Date:  26/07/2023
Detailed Problem: Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 < numbers.length.

Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

Your solution must use only constant extra space.

Example 1:
Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].

Example 2:
Input: numbers = [2,3,4], target = 6
Output: [1,3]
Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].

Example 3:
Input: numbers = [-1,0], target = -1
Output: [1,2]
Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].
"""
class Solution:
    def twoSum(self, numbers: List[int], target: int) -> List[int]:
        slow = 0
        fast = len(numbers)-1

        while slow< fast:
            if numbers[slow] + numbers[fast] == target:
                return [slow+1,fast+1]
                
            elif numbers[slow] + numbers[fast] < target:
                slow +=1
        
            else:
                fast -=1
        return [-1,-1]
"""
Time Complexity:O(n)
Space Complexity: O(1)
"""