Leetcode 3377. Digit Operations to Make Two Integers Equal

• Leetcode 3377. Digit Operations to Make Two Integers Equal
  • 1. 解题思路
  • 2. 代码实现

• 题目链接：3377. Digit Operations to Make Two Integers Equal

1. 解题思路

这一题的核心思路属于路径遍历问题，我们使用一个堆排来控制最优路径的选择。

我们首先全局地给出10000以内的全部素数，然后我们考察当前数据所能获得的全部合法的操作结果，然后用堆排存入之后按照cost进行遍历，直到所有的结果都被遍历过或者找到目标值m为止。

2. 代码实现

给出python代码实现如下：

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

PRIMES = get_primes(10000)

class Solution:
    def minOperations(self, n: int, m: int) -> int:
        if n in PRIMES:
            return -1
        
        l = len(str(n))
        seen = set()
        q = [(n, n)]
        while q:
            cost, n = heapq.heappop(q)
            if n in seen:
                continue
            if n == m:
                return cost
            seen.add(n)
            sn, delta = str(n)[::-1], 1
            for digit in sn:
                if digit != "0" and n-delta not in PRIMES:
                    heapq.heappush(q, (cost + n-delta, n-delta))
                if digit != "9" and n+delta not in PRIMES:
                    heapq.heappush(q, (cost + n+delta, n+delta))
                delta *= 10
        return -1

提交代码评测得到：耗时846ms，占用内存19.6MB。