Remove duplicate elements from sorted array

topic

intput=【1，1，2】
output = 【1，2，X】

Ideas

Double pointer

Code

def removeDuplicates(list1):
    tail = 0
    for i in range(1,len(list1)):
        if list1[tail] != list1[i]:
            tail += 1
            list1[tail] = list1[i]
    tail = tail +1
    while tail<len(list1):
        list1[tail] = 'X'
        tail +=1
    return list1

#A = [0,0,1,1,1,2,2,3,3,4]
A = [1,1,2]
a = removeDuplicates(A)
print(a)