题目：
Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.
Do not allocate extra space for another array, you must do this in place with constant memory.
For example,
Given input array A = [1,1,2],
Your function should return length = 2, and A is now [1,2].
题解：
题目关键字：数组，已排好序的，只能in place替换，不能用额外数组，并且要求结果返回unique的长度。
题解方法是双指针，一个指针只记录unique的并且帮助记录长度，一个指针往前找。
代码如下：
1 public int removeDuplicates(int[] A) {
2 if(A.length == 0 || A == null)
3 return 0;
4
5 int len = 1;
6 for(int index = 1; index < A.length; index++){
7 if(A[index] != A[index-1]){
8 if(A[index] != A[len])
9 A[len] = A[index];
10 len++;
11 }
12 }
13 return len;
14 }
2 if(A.length == 0 || A == null)
3 return 0;
4
5 int len = 1;
6 for(int index = 1; index < A.length; index++){
7 if(A[index] != A[index-1]){
8 if(A[index] != A[len])
9 A[len] = A[index];
10 len++;
11 }
12 }
13 return len;
14 }