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61 lines
2.0 KiB
Markdown
61 lines
2.0 KiB
Markdown
# [27. Remove Element](https://leetcode.com/problems/remove-element/)
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## 题目
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Given an array nums and a value val, remove all instances of that value in-place and return the new length.
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Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
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The order of elements can be changed. It doesn't matter what you leave beyond the new length.
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Example 1:
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```c
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Given nums = [3,2,2,3], val = 3,
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Your function should return length = 2, with the first two elements of nums being 2.
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It doesn't matter what you leave beyond the returned length.
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```
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Example 2:
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```c
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Given nums = [0,1,2,2,3,0,4,2], val = 2,
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Your function should return length = 5, with the first five elements of nums containing 0, 1, 3, 0, and 4.
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Note that the order of those five elements can be arbitrary.
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It doesn't matter what values are set beyond the returned length.
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```
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Clarification:
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Confused why the returned value is an integer but your answer is an array?
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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.
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Internally you can think of this:
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```c
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// nums is passed in by reference. (i.e., without making a copy)
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int len = removeElement(nums, val);
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// any modification to nums in your function would be known by the caller.
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// using the length returned by your function, it prints the first len elements.
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for (int i = 0; i < len; i++) {
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print(nums[i]);
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}
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```
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## 题目大意
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给定一个数组 nums 和一个数值 val，将数组中所有等于 val 的元素删除，并返回剩余的元素个数。
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## 解题思路
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这道题和第 283 题很像。这道题和第 283 题基本一致，283 题是删除 0，这一题是给定的一个 val，实质是一样的。
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这里数组的删除并不是真的删除，只是将删除的元素移动到数组后面的空间内，然后返回数组实际剩余的元素个数，OJ 最终判断题目的时候会读取数组剩余个数的元素进行输出。
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