Two Sum II - Input array is sorted.py

'''
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.
Example:

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.
'''

class Solution(object):
    def twoSum(self, numbers, target):
        """
        :type numbers: List[int]
        :type target: int
        :rtype: List[int]
        """
        
        for i in xrange(len(numbers)):
            if numbers[i] > target / 2:
                break
                
            idx = self.find(numbers, i+1, len(numbers) - 1, target - numbers[i])
            if idx != -1:
                return [i+1, idx+1]
        return [-1, -1]
    
    def find(self, numbers, left, right, t):
        while left <= right:
            mid = (left + right) / 2
            if numbers[mid] < t:
                left = mid + 1
            elif numbers[mid] > t:
                right = mid - 1
            else:
                return mid
            
        return -1