This code defines a class `Solution` with a method `myPow`...
This code defines a class Solution
with a method myPow
that calculates the result of raising a number x
to the power of an integer n
. Here's a detailed breakdown of its functionality:
Code Functionality:
-
Base Cases:
- If
x
is1
orn
is0
, the result is1
(since any number to the power of 0 or 1 raised to any power is 1).
if(x==1 || n==0){ return 1; }
- If
-
Handle the Case When
n == 1
:- If
n == 1
, the result is simplyx
.
if(n==1){ return x; }
- If
-
Handle Negative Powers (
n < 0
):- If
n
is negative, the power can be rewritten as ( \frac{1}{x^{-n}} ). To prevent infinite recursion whenn
is equal toINT_MIN
(the smallest possible integer value), the code handles this special case:- ( \text{myPow}(x, \text{INT_MIN}) = \frac{1}{\text{myPow}(x, \text{INT_MAX}) \cdot x} ).
if(n<0){ if (n == INT_MIN) { return 1 / (myPow(x, INT_MAX) * x); } return 1 / myPow(x, -n); }
- If
-
Efficient Exponentiation Using Recursion:
- The code uses exponentiation by squaring:
- If
n
is even, it reduces the problem by calculatingmyPow(x, n/2)
recursively.
if(n%2==0){ return myPow(x,n/2); }
- If
n
is odd, it reduces the problem by calculating ( x \cdot \text{myPow}(x, n-1) ).
else{ return x*myPow(x,n-1); }
- If
- The code uses exponentiation by squaring:
The Problem with x = 0.00001
, n = 2147483647
(TLE Issue):
The code becomes inefficient for very large values of n
(like 2147483647
), leading to a Time Limit Exceeded (TLE) error. This happens because the recursive calls stack up and are not optimized for such cases. Specifically:
- The logic to compute the result involves excessive recursion due to the naive handling of
n
. - Although the logic divides
n
in half for even powers, it still incurs a large recursion depth proportional to the size ofn
.
Optimizations to Fix TLE:
To resolve the inefficiency, you can use an iterative version or ensure the recursive algorithm handles exponentiation by squaring more effectively:
- Combine the calculations for even and odd powers more explicitly.
- Use an iterative approach to avoid recursion overhead.
For example, an iterative approach might look like this:
double myPowIterative(double x, int n) {
long long power = n;
if (power < 0) {
power = -power;
x = 1 / x;
}
double result = 1;
while (power > 0) {
if (power % 2 == 1) {
result *= x;
}
x *= x;
power /= 2;
}
return result;
}
This approach works efficiently for very large values of n
, avoiding excessive recursion depth and preventing TLE.