27. Remove Element

置顶

Created At : 2021-04-07 23:57

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Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements innums which are not equal toval.

Consider the number of elements in nums which are not equal to val be k, to get accepted, you need to do the following things:

Change the array nums such that the first k elements of nums contain the elements which are not equal to val. The remaining elements of nums are not important as well as the size of nums.
Return k.

Custom Judge:

The judge will test your solution with the following code:

int[] nums = [...]; // Input array
int val = ...; // Value to remove
int[] expectedNums = [...]; // The expected answer with correct length.
                            // It is sorted with no values equaling val.


int k = removeElement(nums, val); // Calls your implementation




assert k == expectedNums.length;  

sort(nums, 0, k); // Sort the first k elements of nums  

for (int i = 0; i < actualLength; i++) {  

assert nums[i] == expectedNums[i];  

}

If all assertions pass, then your solution will be accepted.

Example 1:

**Input:** nums = [3,2,2,3], val = 3
**Output:** 2, nums = [2,2,_,_]
**Explanation:** Your function should return k = 2, with the first two elements of nums being 2.
It does not matter what you leave beyond the returned k (hence they are underscores).

Example 2:

**Input:** nums = [0,1,2,2,3,0,4,2], val = 2
**Output:** 5, nums = [0,1,4,0,3,_,_,_]
**Explanation:** Your function should return k = 5, with the first five elements of nums containing 0, 0, 1, 3, and 4.
Note that the five elements can be returned in any order.
It does not matter what you leave beyond the returned k (hence they are underscores).

Constraints:

0 <= nums.length <= 100
0 <= nums[i] <= 50
0 <= val <= 100

这道题让我们移除一个数组中和给定值相同的数字，并返回新的数组的长度。是一道比较容易的题，只需要一个变量用来计数，然后遍历原数组，如果当前的值和给定值不同，就把当前值覆盖计数变量的位置，并将计数变量加1。代码如下：

class Solution {
public:
    int removeElement(vector<int>& nums, int val) {
        int res = 0;
        for (int i = 0; i < nums.size(); ++i) {
            if (nums[i] != val) nums[res++] = nums[i];
        }
        return res;
    }
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/27

类似题目：

Remove Duplicates from Sorted Array

Remove Linked List Elements

Move Zeroes

参考资料：

https://leetcode.com/problems/remove-element/

https://leetcode.com/problems/remove-element/discuss/12286/Accepted-java-solution

https://leetcode.com/problems/remove-element/discuss/12289/My-solution-for-your-reference.

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