27. Remove Element
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.
把数组中等于val的值移除,然后返回数组长度。要求没有额外空间。
两个指针,一个从左往右,一个从右往左,如果左边的数等于value,和右边交换
class Solution(object): def removeElement(self, nums, val): """ :type nums: List[int] :type val: int :rtype: int """ r = len(nums) - 1 l = 0 while l <= r: if nums[l] == val: nums[l] = nums[r] r -= 1 else: l += 1 return l