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
Solution 1:
public class Solution {
public int integerReplacement(int n) {
if(n==Integer.MAX_VALUE) return 32;
int step = 0;
while(n>1){
if(n%2==0){
n = n>>1;
} else {
if(n==3) n--;
else if((n&3)==3) n++;
else n--;
}
step++;
}
return step;
}
}
Solution 2:
public int integerReplacement(int n) {
int c = 0;
while (n != 1) {
if ((n & 1) == 0) {
n >>>= 1;
} else if (n == 3 || Integer.bitCount(n + 1) > Integer.bitCount(n - 1)) {
--n;
} else {
++n;
}
++c;
}
return c;
}
Solution 3:
public int integerReplacement(int n) {
int c = 0;
while (n != 1) {
if ((n & 1) == 0) {
n >>>= 1;
} else if (n == 3 || ((n >>> 1) & 1) == 0) {
--n;
} else {
++n;
}
++c;
}
return c;
}