Leetcode Problem 823. Binary Trees With Factors

823. Binary Trees With Factors

Leetcode Solutions

Dynamic Programming Approach to Count Factored Binary Trees

  1. Sort the input array arr.
  2. Initialize a hashmap index to store the indices of the elements in arr.
  3. Initialize an array dp of the same length as arr to store the number of trees with each element as the root.
  4. Iterate over the sorted array, and for each element v, set dp[v] to 1 (since each element can form a tree by itself).
  5. For each element v, iterate over the array again to find all pairs x and y such that x * y == v.
  6. For each valid pair, add dp[x] * dp[y] to dp[v].
  7. After processing all elements, sum up all values in dp to get the total number of trees.
  8. Return the total number of trees modulo 10^9 + 7.
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