Question

372. Super Pow

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Description

Your task is to calculate ab mod 1337 where a is a positive integer and b is an extremely large positive integer given in the form of an array.

 

Example 1:

Input: a = 2, b = [3]
Output: 8

Example 2:

Input: a = 2, b = [1,0]
Output: 1024

Example 3:

Input: a = 1, b = [4,3,3,8,5,2]
Output: 1

 

Constraints:

• 1 <= a <= 231 - 1
• 1 <= b.length <= 2000
• 0 <= b[i] <= 9
• b does not contain leading zeros.

Solutions

Solution 1

class Solution:
  def superPow(self, a: int, b: List[int]) -> int:
    mod = 1337
    ans = 1
    for e in b[::-1]:
      ans = ans * pow(a, e, mod) % mod
      a = pow(a, 10, mod)
    return ans

class Solution {
  private final int mod = 1337;

  public int superPow(int a, int[] b) {
    long ans = 1;
    for (int i = b.length - 1; i >= 0; --i) {
      ans = ans * qpow(a, b[i]) % mod;
      a = qpow(a, 10);
    }
    return (int) ans;
  }

  private long qpow(long a, int n) {
    long ans = 1;
    for (; n > 0; n >>= 1) {
      if ((n & 1) == 1) {
        ans = ans * a % mod;
      }
      a = a * a % mod;
    }
    return ans;
  }
}

class Solution {
public:
  int superPow(int a, vector<int>& b) {
    using ll = long long;
    const int mod = 1337;
    ll ans = 1;
    auto qpow = [&](ll a, int n) {
      ll ans = 1;
      for (; n; n >>= 1) {
        if (n & 1) {
          ans = ans * a % mod;
        }
        a = a * a % mod;
      }
      return (int) ans;
    };
    for (int i = b.size() - 1; ~i; --i) {
      ans = ans * qpow(a, b[i]) % mod;
      a = qpow(a, 10);
    }
    return ans;
  }
};

func superPow(a int, b []int) int {
  const mod int = 1337
  ans := 1
  qpow := func(a, n int) int {
    ans := 1
    for ; n > 0; n >>= 1 {
      if n&1 == 1 {
        ans = ans * a % mod
      }
      a = a * a % mod
    }
    return ans
  }
  for i := len(b) - 1; i >= 0; i-- {
    ans = ans * qpow(a, b[i]) % mod
    a = qpow(a, 10)
  }
  return ans
}

function superPow(a: number, b: number[]): number {
  let ans = 1;
  const mod = 1337;
  const qpow = (a: number, n: number): number => {
    let ans = 1;
    for (; n; n >>= 1) {
      if (n & 1) {
        ans = Number((BigInt(ans) * BigInt(a)) % BigInt(mod));
      }
      a = Number((BigInt(a) * BigInt(a)) % BigInt(mod));
    }
    return ans;
  };
  for (let i = b.length - 1; ~i; --i) {
    ans = Number((BigInt(ans) * BigInt(qpow(a, b[i]))) % BigInt(mod));
    a = qpow(a, 10);
  }
  return ans;
}