[LeetCode] Remove Duplicates from Sorted Array

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].

解法：设置两个指针ptr1,和ptr2,其中ptr1指向不重复的数字末尾，ptr2则用来遍历数组，当发现ptr2和它之前指向的数不一致时，就将ptr1++，并将ptr2指向的值赋值给ptr1。当ptr2遍历结束，ptr1指向的就是新数组的末尾，通过指针相减即可得到新数组的长度。

C语言实现：

int removeDuplicates(int* nums, int numsSize) {
    if(NULL == nums)
        return NULL;
    if(numsSize <=1)
        return numsSize;
    int *ptr1,*ptr2;
    int pre,i;
    ptr1 = nums;
    ptr2 = nums;
    for(i=0;i<numsSize-1;i++)
    {
        pre = *ptr2;
        ptr2++;
        if(*ptr2 != pre)
        {
            ptr1++;
            *ptr1 = *ptr2;
        }
    }
    return (ptr1-nums)+1;

}