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. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

这个题目居然是leetcode 1的follow up, 而且是Medium难度，令人难以理解

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