25期代码随想录算法训练营第六天 | 哈希表 part 1

242.有效的字母异位词

链接

class Solution:
    def isAnagram(self, s: str, t: str) -> bool:
        record = [0] * 26
        for i in s:
            #并不需要记住字符a的ASCII，只要求出一个相对数值就可以了
            record[ord(i) - ord("a")] += 1
        for i in t:
            record[ord(i) - ord("a")] -= 1
        for i in range(26):
            if record[i] != 0:
                #record数组如果有的元素不为零0，说明字符串s和t 一定是谁多了字符或者谁少了字符。
                return False
        return True

349. 两个数组的交集

链接

class Solution:
    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
        return list(set(nums1) & set(nums2))

class Solution:
    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
        pool = set()
        res = set()
        for num in nums1:
            pool.add(num)
        
        for num in nums2:
            if num in pool:
                res.add(num)
        
        return list(res)

202. 快乐数

链接

class Solution:
    def isHappy(self, n: int) -> bool:
        pool = set()

        while n != 1:
            res = 0
            for i in str(n):
                res += int(i) ** 2
            
            if res in pool:
                return False
            else:
                pool.add(res)
            
            n = res
        
        return True

1. 两数之和

链接

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        _map = {}

        for i, v in enumerate(nums):
            if v in _map:
                return [i, _map[v]]
            else:
                _map[target - v] = i