397. Integer Replacement

397. Integer Replacement

 

Question
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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

a.

public class Solution {
public int integerReplacement(int n) {
if(n==2147483647)
return 32;
if(n==1)
return 0;
if((n&1)==0)
return integerReplacement(n/2)+1;
else
return min(integerReplacement(n-1)+1,integerReplacement(n+1)+1);
}
static  int min(int i,int j){
return i>j?j:i;
}}

b.public class Solution {
    public int integerReplacement(int n) {
        int step=0;
        while(n!=1){
            if((n&1)==0)
                n>>>=1;
            else if(n==3||(n&3)==1)
                n-=1;
            else
                n+=1;
            step++;    
            }
        return step;    
        
    }
}