26. 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 nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn't matter what you leave beyond the new length.

Array类题目。

注意到超出new length的部分不相关，因此我们不必要shift数组元素，而只需将不重复的元素记录下来即可。 采用two pointers的思想，当发现不重复时，将这个元素放置到相应位置。

public class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        int k = 0;
        for(int i = 1; i < nums.length; i++) {
            if(nums[k] != nums[i]) {
                nums[++k] = nums[i];
            }
        }
        return k+1;
    }
}

同样的思想，不同的implementation。

public int removeDuplicates(int[] nums) {
    int i = 0;
    for(int n : nums)
        if(i < 1 || n > nums[i - 1]) 
            nums[i++] = n;
    return i;
}