268. 缺失数字

268. 缺失数字

题目描述

1.1、使用新的列表

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        ns = [0 for i in range(len(nums) + 1)]
        for i in nums:
            ns[i] = 1
        
        for i in range(len(ns)):
            if ns[i] == 0:
                return i

1.2、索引与数的关系，求和

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        res = len(nums)
        
        for idx, num in enumerate(nums):
            print(idx, num)
            res += idx - num
        return res

1.3、位运算

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        missing = len(nums)
        for i in range(len(nums)):
            missing ^= i ^ nums[i]
        return missing