Easy
https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/description/
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.
/**
* @param {number[]} numbers
* @param {number} target
* @return {number[]}
*/
var twoSum = function(numbers, target) {
// 解法一：由于是有序的，可以通过快慢指针，否则需要先排序
let left = 0;
let right = numbers.length - 1;
while(left < right) {
if(numbers[left] + numbers[right] == target) {
return [left + 1, right + 1]
}
if(numbers[left] + numbers[right] < target) {
left += 1
}
if(numbers[left] + numbers[right] > target) {
right -= 1
}
}
// 解法二：通过记录出现的数字
const visited = {}
for(let i = 0; i < numbers.length; i ++) {
const element = numbers[i]
if(visited[target - element] !== undefined) {
return [visited[target - element], i + 1]
}
visited[element] = i + 1
}
return []
};