50. Pow(x, n)

class Solution {
    public double myPow(double x, int n) {
        
        if (n == 0) {
            return 1.0;
        }
        double result = x; 
        
        int i = 1;
        while(i < Math.abs(n)) {
            result *= x;
            i++;
        }
        
        if (n < 0) result = 1 / result;
        
        return result; 
    }
}

Time limit exceeded
299 / 304 test cases passed.

반띵하는 방식을 생각해냄 (logn)

class Solution {
    public double myPow(double x, int n) {
        
        if (n == 0) {
            return 1.0;
        }
        
        double result = 1; 
        
        int i = Math.abs(n);
        
        double multiple = x; 
        while(i > 0) {
            if (i % 2 == 1) {
                result = result * multiple;
            }
            
            multiple = multiple * multiple; 
            
            i = i / 2;
        }
        
        if (n < 0) result = 1 / result;
        
        return result; 
    }
}

진심 개 거지같은 케이스 하나 통과 안됨..
303 / 304 test cases passed.
Status: Wrong Answer

2.00000
-2147483648

외죠?

class Solution {
    public double myPow(double x, int n) {
        
        if (n == 0) {
            return 1.0;
        }
        
        long N = n;
        
        if (N < 0) {
            x = 1 / x;
            N = -N; 
        }
        
        double result = 1; 
        

        
        double multiple = x; 
        while(N > 0) {
            if (N % 2 == 1) {
                result = result * multiple;
            }
            
            multiple = multiple * multiple; 
            
            N = N / 2;
        }
        
        return result; 
    }
}

Runtime: 0 ms, faster than 100.00% of Java online submissions for Pow(x, n).
Memory Usage: 38.5 MB, less than 32.56% of Java online submissions for Pow(x, n).

루션이 나랑 같은거 같은데 걍 long으로만 바꿔줌... 뭐하자는것?