Leetcode Problem 2787. Ways to Express an Integer as Sum of Powers

2787. Ways to Express an Integer as Sum of Powers

Leetcode Solutions

Dynamic Programming with Memoization

  1. Initialize a memoization table dp with default values of -1.
  2. Define a recursive function helper(base, n, x, dp) that returns the number of ways to express n using powers of integers starting from base to n.
  3. If n is 0, return 1 as we have found a valid combination.
  4. If base raised to the power x is greater than n, return 0 as we cannot include base in our sum.
  5. If the result is already computed in dp[base][n], return that value.
  6. Calculate val as base raised to the power x.
  7. Recursively call helper to include base in the sum and to exclude base from the sum.
  8. Store the sum of include and exclude in dp[base][n] modulo 10^9 + 7.
  9. Return dp[base][n].
  10. Call helper(1, n, x, dp) to start the recursion from base 1.
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Iterative Bottom-Up Dynamic Programming

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