LeetCode-array2

Title:

Two Sum II - Input array is sorted

Related Topics:

Array , Binary Search, Two Pointers

Describe:

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2.

Note:

Your returned answers (both index1 and index2) are not zero-based.
You may assume that each input would have exactly one solution and you may not use the same element twice.

Sample Input&output:

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.

Code:

class Solution(object):
    def twoSum(self, numbers, target):
        """
        :type numbers: List[int]
        :type target: int
        :rtype: List[int]
        """
        n = len(numbers)
        for i in range(n-1, -1, -1):
            if numbers[i]<=target or target<=0:
                for j in range(i-1, -1, -1):
                    if numbers[i]+numbers[j]==target:
                        two = []
                        two.append(j+1)
                        two.append(i+1)
                        return two