# 397. Integer Replacement

## Description

Given a positive integer n, you can apply one of the following operations:

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

Return the minimum number of operations needed for n to become 1.

Example 1:

Input: n = 8
Output: 3
Explanation: 8 -> 4 -> 2 -> 1


Example 2:

Input: n = 7
Output: 4
Explanation: 7 -> 8 -> 4 -> 2 -> 1
or 7 -> 6 -> 3 -> 2 -> 1


Example 3:

Input: n = 4
Output: 2


Constraints:

• 1 <= n <= 231 - 1

## Solutions

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

• class Solution {
public:
int integerReplacement(int N) {
int ans = 0;
long n = N;
while (n != 1) {
if ((n & 1) == 0)
n >>= 1;
else if (n != 3 && (n & 3) == 3)
++n;
else
--n;
++ans;
}
return ans;
}
};

• class Solution:
def integerReplacement(self, n: int) -> int:
ans = 0
while n != 1:
if (n & 1) == 0:
n >>= 1
elif n != 3 and (n & 3) == 3:
n += 1
else:
n -= 1
ans += 1
return ans


• func integerReplacement(n int) int {
ans := 0
for n != 1 {
if (n & 1) == 0 {
n >>= 1
} else if n != 3 && (n&3) == 3 {
n++
} else {
n--
}
ans++
}
return ans
}