leetcode刷题记录471-480 python版

前言

继续leetcode刷题生涯
这里记录的都是笔者觉得有点意思的做法
参考了好几位大佬的题解，尤其是powcai大佬和labuladong大佬，感谢各位大佬

472. 连接词

# 排序，看前面的在不在
class Solution:
    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
        words.sort(key=len)
        min_len = max(1, len(words[0]))
        prev = set()
        res = []
        def check(word):
    		if word in prev: return True
    		for i in range(min_len, len(word) - min_len + 1):
        		if word[:i] in prev and check(word[i:]):
           		return True
    		return False
	for word in words:
		if check(word):
		    res.append(word)
		prev.add(word)
	return res

473. 火柴拼正方形

class Solution:
    def makesquare(self, nums: List[int]) -> bool:
        if len(nums) < 4: return False
        div, mod = divmod(sum(nums), 4)
        if mod != 0: return False
        nums.sort(reverse=True)
        edges = [0] * 4
        def dfs(i):
            if i == len(nums):
                if len(set(edges)) == 1:
                    return True
                return False
            for k in range(4):
                if edges[k] + nums[i] > div: continue
                edges[k] += nums[i]
                if dfs(i + 1): return True
                edges[k] -= nums[i]
            return False
        return dfs(0)

474. 一和零

# dp
class Solution:
    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
        dp = [[[0] * (n + 1) for _ in range(m + 1)] for _ in range(len(strs) + 1)]
        for i in range(1, len(strs) + 1):
            ones = strs[i - 1].count("1")
            zeros = strs[i - 1].count("0")
            for j in range(m + 1):
                for k in range(n + 1):
                    dp[i][j][k] = dp[i - 1][j][k]
                    if j >= zeros and k >= ones and dp[i][j][k] < dp[i - 1][j - zeros][k - ones] + 1:
                        dp[i][j][k] = dp[i - 1][j - zeros][k - ones] + 1
        return dp[-1][-1][-1]

475. 供暖器

class Solution:
    def findRadius(self, houses: List[int], heaters: List[int]) -> int:
        houses.sort()
        heaters.sort()
        heaters = [float("-inf")] + heaters + [float("inf")]
        i = 1
        res = 0
        for house in houses:
            while i < len(heaters) - 1 and house > heaters[i]:
                i += 1
            res = max(res, min(heaters[i] - house, house - heaters[i - 1]))
        return res

476. 数字的补数

class Solution:
    def findComplement(self, num: int) -> int:
        return 2**(len(bin(num))-2)-num-1

477. 汉明距离总和

class Solution:
    def totalHammingDistance(self, nums: List[int]) -> int:
        res, n = 0, len(nums)
        for i in range(32):
            cnt = 0
            for j in range(n):
                cnt += (nums[j] >> i) & 1
            res += (n - cnt) * cnt
        return res 

478. 在圆内随机生成点

# 极坐标
import math
import random
class Solution:
    def __init__(self, radius: float, x_center: float, y_center: float):
        self.radius = radius
        self.x_center = x_center
        self.y_center = y_center
    def randPoint(self) -> List[float]:
        l = self.radius * math.sqrt(random.random())
        deg = random.random() * math.pi * 2
        x = l * math.cos(deg) + self.x_center
        y = l * math.sin(deg) + self.y_center
        return [x, y]

479. 最大回文数乘积

# 打表了
class Solution:
    def largestPalindrome(self, n: int) -> int:
        return [9,987,123,597,677,1218,877,475][n-1]

480. 滑动窗口中位数

class Solution:
    def medianSlidingWindow(self, nums: List[int], k: int) -> List[float]:
        import bisect
        arr = []
        left = 0
        res = []
        for right in range(len(nums)):
            bisect.insort(arr, nums[right])
            while len(arr) > k:
                arr.pop(bisect.bisect_left(arr, nums[left]))
                left += 1
            if len(arr) == k:
                res.append((arr[k // 2] + arr[(k - 1) // 2]) / 2.0)
        return res