LeetCode 0397 - Integer Replacement

Reck Zhang

发布于 2021-08-11 11:08:11

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发布于 2021-08-11 11:08:11

文章被收录于专栏：Reck Zhang

Integer Replacement

Desicription

Given a positive integer n and you can do operations as follow:

If n is even, replace n with n/2.
If n is odd, you can replace n with either n + 1 or n - 1.

What is the minimum number of replacements needed for n to become 1?

Example 1:

Input:
8

Output:
3

Explanation:
8 -> 4 -> 2 -> 1

Example 2:

Input:
7

Output:
4

Explanation:
7 -> 8 -> 4 -> 2 -> 1
or
7 -> 6 -> 3 -> 2 -> 1

Solution

class Solution {
private:
    std::unordered_map<long long , long long> map = std::unordered_map<long long, long long>{};
public:
    int integerReplacement(long long n) {
        if(n == 1) {
            return 0;
        }

        if(map[n] == 0) {
            if(n & 1 == 1) {
                map[n] = 2 + std::min(integerReplacement((n + 1) / 2), integerReplacement((n - 1) / 2));
            } else {
                map[n] = 1 + integerReplacement(n / 2);
            }
        }

        return map[n];
    }
};

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原始发表：2019-09-30，如有侵权请联系 cloudcommunity@tencent.com 删除

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