Question

397. Integer Replacement

中文文档

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

Solution 1

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

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;
  }
};

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
}