Leetcode-397:integer Replacement (1 steps for integer change)

Title:

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

If N is a even, replace N with N/2.
If N is the odd, you can replace n with either n + 1 or n-1.
What's the minimum number of replacements needed for N to become 1? Example:

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
-&G T 2-1

Problem Resolution:

Given an integer n, the integer is progressively replaced with 1. If an even number is replaced with N/2, an odd number can be replaced with n+1 or n-1. To find the smallest replacement step. Links: leetcode:https://leetcode.com/problems/integer-replacement/description/ Idea label

Mathematical Thinking , dynamic planning , recursive (timeout) answer: The topic seems very easy, but in the process will encounter a lot of problems. Using a simple recursive process, time-outs, high complexity, and math to simplify the recursive process:
Each operation is changed to the next array, and +1, so we record the number of changes can be, when n is even, the direct substitution of N/2, when n is odd, if (n+1)% 4 = = 0, that is, n+1 is a multiple of 4, then n+1 replacement is a step that can be reduced In other cases, replacing with n-1 is always minimal. In addition, the maximum value of int is 2^32-1, so if you use the above method +1 directly, then the programming 2^32 overflow, so we need to deal with this situation separately. Make Int_max to express.

Class Solution {public
:
    int integerreplacement (int n) {
        if (n = = Int_max) return;

        int count = 0;
        while (n > 1) {
            if (n% 2 = = 0)
                n = n/2;
            else{
                if ((n+1)%4 = = 0 && (n-1! = 2))
                    n++;
                else
                    n--;
            }
            count++;
        }

        return count;
    }
};