LeetCode26. Remove Duplicates from Sorted Array

Given a sorted array nums, 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 by modifying the input array in-place with O(1) extra memory.

Example 1:

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Given 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 returned length.

Example 2:

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Given nums = [0,0,1,1,1,2,2,3,3,4],

Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively.

It doesn't matter what values are set beyond the returned length.

Clarification:

Confused why the returned value is an integer but your answer is an array?

Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.

Internally you can think of this:

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// nums is passed in by reference. (i.e., without making a copy)
int len = removeDuplicates(nums);

// any modification to nums in your function would be known by the caller.
// using the length returned by your function, it prints the first len elements.
for (int i = 0; i < len; i++) {
print(nums[i]);
}

Two pointers

my code in cpp

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int removeDuplicates(vector<int>& nums) {
if (nums.empty()) return 0;
int _new = 0;
for (int _old = 1; _old < nums.size(); _old++)
if (nums[_old] != nums[_new]) nums[++_new] = nums[_old];
return _new+1;
}

总结

未命名5

  1. 双指针,一个指向老数组,一个指向新数组。如果老数组指针的值不等于新数组指针的值,新数组向前移一格。就是把[27] 移除元素的target变成nums[_new]了。
  2. 另外记得做入口检查。
Thanks for Support.