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
orn - 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
The most straightforward way is to use recursion. Recursively calculate number of replacement needed until integer reaches 1.
public int integerReplacement(int n) { return getCount(n, 0); } private int getCount(long n, int count) { if (n == 1) { return count; } count++; if (n % 2 == 0) { return getCount(n / 2, count); } else { return Math.min(getCount(n - 1, count), getCount(n + 1, count)); } }
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