README_EN.md

167. Two Sum II - Input array is sorted

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Description

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

Return the indices of the two numbers (1-indexed) as an integer array answer of size 2, where 1 <= answer[0] < answer[1] <= numbers.length.

You may assume that each input would have exactly one solution and you may not use the same element twice.

 

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.

Example 2:

Input: numbers = [2,3,4], target = 6
Output: [1,3]

Example 3:

Input: numbers = [-1,0], target = -1
Output: [1,2]

 

Constraints:

• 2 <= numbers.length <= 3 * 104
• -1000 <= numbers[i] <= 1000
• numbers is sorted in increasing order.
• -1000 <= target <= 1000
• Only one valid answer exists.

Solutions

Python3

class Solution:
    def twoSum(self, numbers: List[int], target: int) -> List[int]:
        left, right = 0, len(numbers) - 1
        while left < right:
            if numbers[left] + numbers[right] == target:
                return [left + 1, right + 1]
            if numbers[left] + numbers[right] < target:
                left += 1
            else:
                right -= 1
        return [-1, -1]

Java

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int left = 0, right = numbers.length - 1;
        while (left < right) {
            if (numbers[left] + numbers[right] == target) {
                return new int[]{left + 1, right + 1};
            }
            if (numbers[left] + numbers[right] < target) {
                ++left;
            } else {
                --right;
            }
        }
        return new int[]{-1, -1};
    }
}

TypeScript

function twoSum(numbers: number[], target: number): number[] {
    for (let right = numbers.length - 1; right >= 0; --right) {
        let left = numbers.indexOf(target - numbers[right]);
        if (left > -1 && left < right) {
            return [left + 1, right + 1];
        }
    }
    return [-1, -1];
}

C++

class Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        int left = 0, right = numbers.size() - 1;
        while (left < right) {
            if (numbers[left] + numbers[right] == target) {
                return {left + 1, right + 1};
            }
            if (numbers[left] + numbers[right] < target) ++left;
            else --right;
        }
        return {-1, -1};
    }
};

Go

func twoSum(numbers []int, target int) []int {
	left, right := 0, len(numbers)-1
	for left < right {
		if numbers[left]+numbers[right] == target {
			return []int{left + 1, right + 1}
		}
		if numbers[left]+numbers[right] < target {
			left++
		} else {
			right--
		}
	}
	return []int{-1, -1}
}

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