Dynamic programming (DP) is a powerful technique used to solve a wide range of optimization problems, but it is not universally applicable to all optimization problems. The applicability of dynamic programming depends on certain key characteristics of the problem. Here are the reasons why dynamic programming can or cannot be applied to a problem:
When Dynamic Programming Can Be Applied
Optimal Substructure: The problem can be broken down into smaller subproblems, and the solution to the original problem can be constructed from the solutions to the subproblems. If an optimal solution to the problem contains optimal solutions to its subproblems, the problem exhibits optimal substructure.
Overlapping Subproblems: The problem should have overlapping subproblems, meaning that the same subproblems are solved multiple times. Dynamic programming is effective when these subproblems can be stored and reused to avoid redundant calculations.
Finite Number of States: There should be a finite number of subproblems. DP algorithms typically build a table of solutions for subproblems, so the number of subproblems should be manageable and finite.
When Dynamic Programming Cannot Be Applied
Lack of Optimal Substructure: If a problem does not have an optimal substructure, then dynamic programming cannot be used. For example, if the optimal solution to a problem does not include the optimal solutions to its subproblems, DP is not suitable.
Non-overlapping Subproblems: If the subproblems are independent and do not overlap, then memoization and reuse of subproblem solutions are not possible, making dynamic programming ineffective.
Infinite Number of States: If a problem has an infinite number of subproblems or states, it is impractical to use dynamic programming because it would require infinite memory and computational power.