Problem
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.
Solution 1
/**
* @param {number[]} numbers
* @param {number} target
* @return {number[]}
*/
var twoSum = function(numbers, target) {
var sum = 0;
var left = 0;
var right = numbers.length - 1;
while (left < right) {
sum = numbers[left] + numbers[right];
if (sum === target) {
return [left + 1, right + 1];
} else if (sum > target) {
right--;
} else {
left++;
}
}
};
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(1).