题目要求
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
思路和代码
可以发现除二后所得到的结果一定优于加减 1。因此，如果当前奇数除二为偶数，则直接做除法，否则将当前奇数加一再除以二，得到偶数的结果。
public int integerReplacement(int n) {
int count = 0;
while(n != 1){
if((n & 1) == 0){
n >>>= 1;
}
else if(n == 3 || ((n>>>1) & 1) == 0){
n–;
}
else{
n++;
}
count++;
}
return count;
}