实现如下编程题目：
1.判断字符串是否是回文？
描述
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
For example,"A man, a plan, a canal: Panama" is a palindrome. "race a car" is not a palindrome.
Note: Have you consider that the string might be empty? This is a good question to ask during an interview.
For the purpose of this problem, we define empty string as valid palindrome.

boolean isPalindrome(String s){  
}

2.找两个数字，使得这两个数字之和等于目标数字
描述
Given an array of integers, 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

int[] twoSum(int[] nums, int target) {  
}