This code defines a function within a `Solution` class that...

July 2, 2025 at 04:28 PM

class Solution { public: double myPow(double x, int n) { if(x==1 || n==0){ return 1; } if(n==1){ return x; } if(n<0){ return 1/myPow(x,n); } if(n%2==0){ return myPow(x,n/2); } else{ return x*myPow(x,n-1); } } };

This code defines a function within a Solution class that calculates ( x^n ) (x raised to the power of n) using a recursive approach. Here's a step-by-step explanation of what it does:

Breakdown:

  1. Base cases:

    • If x == 1 or n == 0, the result is 1 because any number raised to the power of 0 is 1, and 1 raised to any power is always 1.
    • If n == 1, the result is x because any number raised to the power of 1 is itself.
  2. Handling negative powers:

    • When n < 0, the function recognizes this and calculates ( x^n ) as ( 1 / (x^n) ). This corresponds to the mathematical property that ( x^{-n} = \frac{1}{x^n} ).
  3. Handling even powers:

    • If n % 2 == 0 (i.e., n is even), the function exploits the property of exponents ( x^n = (x^{n/2})^2 ). Instead of directly computing ( x^n ), the function recursively calls itself with n / 2, which reduces the computational complexity.
  4. Handling odd powers:

    • If none of the other conditions apply, it means n is odd. The function uses the property ( x^n = x \times x^{n-1} ) to recursively compute the result by reducing the problem to calculating ( x^{n-1} ).

Concerns:

  • Infinite recursion for negative powers: The code for handling negative powers (return 1 / myPow(x, n);) is incorrect and causes infinite recursion because it doesn't update the n value in the recursive call (it keeps passing the negative n). It should instead convert n to positive by passing -n.

Fixed Code:

You can fix the infinite recursion issue for negative n like this:

if (n < 0) {
    return 1 / myPow(x, -n);
}

Key Properties Used:

  1. ( x^0 = 1 )
  2. ( x^n = x \times x^{n-1} ) (for odd n)
  3. ( x^n = (x^{n/2}) \times (x^{n/2}) ) (for even n)

Computational Efficiency:

This implementation uses recursion and halves the problem size for even powers, leading to a time complexity of ( O(\log n) ), making it efficient for computing powers.

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