Leetcode 3044. Most Frequent Prime

• Leetcode 3044. Most Frequent Prime
  • 1. 解题思路
  • 2. 代码实现

• 题目链接：3044. Most Frequent Prime

1. 解题思路

这一题的话思路上倒是没啥，直接遍历一下每一个点作为起点时8个方向上所能找到的全部质数然后count一下他们出现的总次数即可。

2. 代码实现

给出python代码实现如下：

def get_primes(n):
    status = [0 for _ in range(n+1)]
    primes = set()
    for i in range(2, n+1):
        if status[i] != 0:
            continue
        primes.add(i)
        for j in range(i, n+1, i):
            status[j] = 1
    return primes

PRIMES = get_primes(10**7)

class Solution:
    def mostFrequentPrime(self, mat: List[List[int]]) -> int:
        n, m = len(mat), len(mat[0])
        
        def get_number(point, direction):
            x, y = point
            s, ans = 0, []
            while 0 <= x < n and 0 <= y < m:
                s = s * 10 + mat[x][y]
                if s >= 10:
                    ans.append(s) 
                x += direction[0]
                y += direction[1]
            return ans
        
        cnt = defaultdict(int)
        for i in range(n):
            for j in range(m):
                for direction in [(0, 1), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, 0), (-1, -1)]:
                    nums = get_number((i, j), direction)
                    for num in nums:
                        if num in PRIMES:
                            cnt[num] += 1
        res = sorted(cnt.items(), key=lambda x: (x[1], x[0]), reverse=True)
        return res[0][0] if res else -1

提交代码评测得到：耗时1286ms，占用内存163.4MB。