167. Two Sum II - Input Array Is Sorted

Problem Description

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.

Examples

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].

def twoSum(numbers: List[int], target: int) -> List[int]:
    left, right = 0, len(numbers) - 1
    
    while left < right:
        current_sum = numbers[left] + numbers[right]
        
        if current_sum == target:
            return [left + 1, right + 1]
        elif current_sum < target:
            left += 1
        else:
            right -= 1
    
    return []  # No solution found

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int left = 0;
        int right = numbers.length - 1;
        
        while (left < right) {
            int currentSum = numbers[left] + numbers[right];
            
            if (currentSum == target) {
                return new int[]{left + 1, right + 1};
            } else if (currentSum < target) {
                left++;
            } else {
                right--;
            }
        }
        
        return new int[]{};  // No solution found
    }
}

class Solution {
public:
    vector twoSum(vector& numbers, int target) {
        int left = 0;
        int right = numbers.size() - 1;
        
        while (left < right) {
            int currentSum = numbers[left] + numbers[right];
            
            if (currentSum == target) {
                return {left + 1, right + 1};
            } else if (currentSum < target) {
                left++;
            } else {
                right--;
            }
        }
        
        return {};  // No solution found
    }
};

/**
 * @param {number[]} numbers
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(numbers, target) {
    let left = 0;
    let right = numbers.length - 1;
    
    while (left < right) {
        const currentSum = numbers[left] + numbers[right];
        
        if (currentSum === target) {
            return [left + 1, right + 1];
        } else if (currentSum < target) {
            left++;
        } else {
            right--;
        }
    }
    
    return [];  // No solution found
};

public class Solution {
    public int[] TwoSum(int[] numbers, int target) {
        int left = 0;
        int right = numbers.Length - 1;
        
        while (left < right) {
            int currentSum = numbers[left] + numbers[right];
            
            if (currentSum == target) {
                return new int[]{left + 1, right + 1};
            } else if (currentSum < target) {
                left++;
            } else {
                right--;
            }
        }
        
        return new int[]{};  // No solution found
    }
}