[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].

用兩根指針分別掃描，一個記錄當前的新數組長度，一個從前往后掃描數組，由於排序過，所以記錄每次新出現的數，發現一個數和當前數不一樣了，則做更新。O(n)

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (n == 0)
            return 0;
            
        int start = 0;
        int key = A[0];
        for(int i = 0; i < n; i++)
            if (A[i] != key)
            {
                A[start++] = key;
                key = A[i];                
            }
            
        A[start++] = key;
        
        return start;
    }
};