167.Two-Sum-II---Input-array-is-sorted

167. Two Sum II Input array is sorted

题目地址

https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/

题目描述

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.

代码

Approach #1 Two Pointer

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