Leetcode Problem 1575. Count All Possible Routes

1575. Count All Possible Routes

Leetcode Solutions

Recursive Dynamic Programming with Memoization

  1. Define a 2D memoization array memo with dimensions [locations.length][fuel + 1] initialized to -1.
  2. Implement a recursive function dfs that takes the current city and remaining fuel as parameters.
    • If the remaining fuel is less than 0, return 0.
    • If the current city is the finish city, return 1.
    • If the result is already computed in memo, return the stored value.
    • Otherwise, iterate over all cities and for each city, recursively call dfs with the new city and updated fuel.
    • Sum the results of these recursive calls and store the result in memo before returning it.
  3. Call the dfs function with the start city and initial fuel.
  4. Return the result modulo 10^9 + 7.
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Iterative Dynamic Programming

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