167. Two Sum II - Input array is sorted【Easy】【双指针-有序数组求两数之和为目标值的下标】

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.
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https://www.cnblogs.com/Roni-i/p/7774100.html

https://www.cnblogs.com/Roni-i/p/9253303.html

几百年前就会双指针了，但是Java有些语法还不熟练。。

（ps：双指针利用序列的递增性

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