27. 移除元素

 

代码一：

class Solution(object):
    def removeElement(self, nums, val):
        """
        :type nums: List[int]
        :type val: int
        :rtype: int
        """
        if nums == []:
            return 0
        i, j = 0, len(nums) - 1

        while i < j:
            if nums[i] != val:
                i += 1
            elif nums[j] == val:
                j -= 1
            elif nums[i] == val:
                nums[i], nums[j] = nums[j], nums[i]
                i += 1
                j -= 1
        # print(nums, i, j)
        if nums[i] == val:
            return len(nums[:i])
        else:
            return len(nums[:i])+1

代码二：

class Solution(object):
    def removeElement(self, nums, val):
        """
        :type nums: List[int]
        :type val: int
        :rtype: int
        """
        if len(nums) == 0:
            return 0
        # 双指针
        i, j = 0, len(nums) - 1
        while i < j:
            # j指向的等于val，j前移
            if nums[j] == val:
                j -= 1
                continue
            # 如果i指向的等于val，交换i和j的值，j前移
            if nums[i] == val:
                nums[i], nums[j] = nums[j], nums[i]
                j -= 1
            # i每一趟都后移
            i += 1
        # print(nums, i, j)
        if nums[i] == val:
            return len(nums[:i])
        else:
            return len(nums[:i]) + 1