# Two Sum II – Input Array Is Sorted LeetCode Solution | Easy Approach Share:

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.

Time: O(n)
Space: O(1)

### 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};
}
};
``````

### 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};
}
}
``````

### Python

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

while l < r:
sum = numbers[l] + numbers[r]
if sum == target:
return [l + 1, r + 1]
if sum < target:
l += 1
else:
r -= 1
``````

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