An integer n is a power of two, if there exists an integer x such that n == 2x.
Example 1:
Input: n = 1
Output: true
Explanation: 20 = 1
Example 2:
Input: n = 16
Output: true
Explanation: 24 = 16
Example 3:
Input: n = 3
Output: false
Constraints:
-231 <= n <= 231–1
Follow up: Could you solve it without loops/recursion?231. Power of Two
Solved
Easy
Topics
Companies
Given an integer n, return true if it is a power of two. Otherwise, return false.
An integer n is a power of two, if there exists an integer x such that n == 2x.
Example 1:
Input: n = 1
Output: true
Explanation: 20 = 1
Example 2:
Input: n = 16
Output: true
Explanation: 24 = 16
Example 3:
Input: n = 3
Output: false
Constraints:
-231 <= n <= 231–1
Follow up: Could you solve it without loops/recursion?
class Solution {
//Time Limit Exceed
public boolean isPowerOfTwo1(int n) {
int m=1;
while(m<n){
m*=2;
}
return m==n?true:false;
}
public boolean isPowerOfTwo2(int n) {
return rec(n,1);
}
boolean rec(int n, int m){
if(n==m) return true;
if(m<n) return rec(n,m*2);
return false;
}
/**
Time :O(1) Space : O(1)
The fact that every power of two contains only one set bit and LSB
1 ---> 0001
2 ---> 00010
4 ----> 00100
8 ----> 01000
*/
public boolean isPowerOfTwo(int n) {
return n>0 &&( (n & (n-1))==0);
}
}
/**
231. Power of Two
Solved
Easy
Topics
Companies
Given an integer n, return true if it is a power of two. Otherwise, return false.
An integer n is a power of two, if there exists an integer x such that n == 2x.
Example 1:
Input: n = 1
Output: true
Explanation: 20 = 1
Example 2:
Input: n = 16
Output: true
Explanation: 24 = 16
Example 3:
Input: n = 3
Output: false
Constraints:
-231 <= n <= 231 - 1
Follow up: Could you solve it without loops/recursion?
*/
