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(N)*- 空间复杂度: O(N)***
算法来源于知乎文章——趣味算法思想 * 由于数组是有序的，所以可以从两边向中间逐渐收敛地进行查找，好处在于避免了双重循环 * 如果最两端的和小于目标数，则可以让左侧下标+1，然后重新进行运算比较 * 如果最两端的和大于目标数，则可以让右侧下标-1，然后重新进行运算比较
代码：
/**
* @param {number[]} numbers
* @param {number} target
* @return {number[]}
*/
var twoSum = function(nums, target) {
var number=[];
var left = 0;
var right = nums.length - 1 ;
while(left < right ) {
if(nums[left] + nums[right] === target) {
return [left+1, right+1]
} else if(nums[left] + nums[right] > target ) {
right--;
} else {
left++;
}
}
};
