167. Two Sum II – Input Array Is Sorted LeetCode Solution

In this guide, you will get 167. Two Sum II – Input Array Is Sorted LeetCode Solution with the best time and space complexity. The solution to Two Sum II – Input Array Is Sorted problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Problem Statement
Complexity Analysis
Two Sum II – Input Array Is Sorted solution in C++
Two Sum II – Input Array Is Sorted solution in Java
Two Sum II – Input Array Is Sorted solution in Python
Additional Resources

167. Two Sum II - Input Array Is Sorted LeetCode Solution image

Problem Statement of Two Sum II – Input Array Is Sorted

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].

Constraints:

2 <= numbers.length <= 3 * 104
-1000 <= numbers[i] <= 1000
numbers is sorted in non-decreasing order.
-1000 <= target <= 1000
The tests are generated such that there is exactly one solution.

Complexity Analysis

Time Complexity: O(n)
Space Complexity: O(1)

167. Two Sum II – Input Array Is Sorted LeetCode Solution in C++

class Solution {
 public:
  vector<int> twoSum(vector<int>& numbers, int target) {
    int l = 0;
    int r = numbers.size() - 1;

    while (numbers[l] + numbers[r] != target)
      if (numbers[l] + numbers[r] < target)
        ++l;
      else
        --r;

    return {l + 1, r + 1};
  }
};
/* code provided by PROGIEZ */

167. Two Sum II – Input Array Is Sorted LeetCode Solution in Java

class Solution {
  public int[] twoSum(int[] numbers, int target) {
    int l = 0;
    int r = numbers.length - 1;

    while (numbers[l] + numbers[r] != target)
      if (numbers[l] + numbers[r] < target)
        ++l;
      else
        --r;

    return new int[] {l + 1, r + 1};
  }
}
// code provided by PROGIEZ

167. Two Sum II – Input Array Is Sorted LeetCode Solution in Python

class Solution:
  def twoSum(self, numbers: list[int], target: int) -> list[int]:
    l = 0
    r = len(numbers) - 1

    while l < r:
      summ = numbers[l] + numbers[r]
      if summ == target:
        return [l + 1, r + 1]
      if summ < target:
        l += 1
      else:
        r -= 1
 # code by PROGIEZ