27. Remove Element
題目
Given an array nums and a value val, remove all instances of that value in-place 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.
The order of elements can be changed. It doesn't matter what you leave beyond the new length.
Example 1:
Given nums = [3,2,2,3], val = 3,
Your function should return length = 2, with the first two elements of nums being 2.
It doesn't matter what you leave beyond the returned length.
Example 2:
Given nums = [0,1,2,2,3,0,4,2], val = 2,
Your function should return length = 5, with the first five elements of nums containing 0, 1, 3, 0, and 4.
Note that the order of those five elements can be arbitrary.
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:
// nums is passed in by reference. (i.e., without making a copy)
int len = removeElement(nums, val);
// 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]);
}
題目大意
給定一個數組 nums 和一個數值 val，將數組中所有等於 val 的元素刪除，並返回剩餘的元素個數。
解題思路
這道題和第 283 題很像。這道題和第 283 題基本一致，283 題是刪除 0，這一題是給定的一個 val，實質是一樣的。
這里數組的刪除並不是真的刪除，只是將刪除的元素移動到數組後面的空間內，然後返回數組實際剩餘的元素個數，OJ 最終判斷題目的時候會讀取數組剩餘個數的元素進行輸出。
來源
- https://books.halfrost.com/leetcode/ChapterFour/0001~0099/0027.Remove-Element/
- https://leetcode-cn.com/problems/remove-element/
- https://mp.weixin.qq.com/s/wj0T-Xs88_FHJFwayElQlA
解答
package removeelement
/*
雙指針法
雙指針法（快慢指針法）在數組和鍊錶的操作中是非常常見的，很多考察數組和鍊錶操作的面試題，都使用雙指針法
*/
func RemoveElementDoublePoint(nums []int, val int) int {
if len(nums)