167. Two Sum II - Input array is sorted
难度: Easy
刷题内容
原题连接
- https://leetcode.com/problems/two-sum-ii-input-array-is-sorted
内容描述
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.
解题方案
思路 1 **- 时间复杂度: O(log2 N)*- 空间复杂度: O(n)***
- 使用贪心算法，用左右的数字开始加，如果数字大于目标right--，反之left++
代码：
/**
* @param {number[]} numbers
* @param {number} target
* @return {number[]}
*/
var twoSum = function(numbers, target) {
if(numbers.length===0)
return [];
var left = 0,right = numbers.length-1;
while(right>left){
if(numbers[right]+numbers[left]>target)
right--;
else if(numbers[right]+numbers[left]<target)
left++;
else return [left+1,right+1];
}
return [];
};
