Coin Change Problem (Total ways to achieve a specific coin denomination)

The Coin Change Problem is a well-known issue within the realm of Dynamic Programming in computer science. In this problem, you are presented with a specific amount and a collection of coin denominations. Your task is to determine the total number of distinct ways to reach that amount using the coins available in those denominations. It is important to emphasize that you have an unlimited supply of each type of coin. Here are some important points that might assist you in solving this problem: Considering the nature of the problem, a brute-force approach would involve listing all possible coin combinations to achieve the total, but this method can be computationally intensive. A more efficient alternative would be to apply dynamic programming, which involves storing the results of sub-problems to prevent redundant calculations. Additionally, be sure to address edge cases, such as scenarios where no combination of coins can total the specified amount or when the amount is zero.

You can implement a solution in Python using Dynamic Programming in the following way: def coinChange ( coins , amount ) : # Create a dp array to keep track of the number of combinations for all amounts up to the specified amount dp = [ 0 ] * ( amount + 1 ) # The total number of ways to achieve the amount of 0 is always 1 dp [ 0 ] = 1 # Iterate through each coin for coin in coins : # Adjust the number of combinations for each possible amount that is equal to or greater than the coin value for x in range ( coin , amount + 1 ) : dp [ x ] += dp [ x - coin ] # The total number of ways to form the specified amount is found at dp[amount] return dp [ amount ] This function sets up a dp array that records the number of combinations for each amount up to the target amount. It then iterates through each coin, updating the dp array values by adding the previously calculated combinations (for the amount lessened by the current coin's value) to the current combinations. Finally, the value at dp[amount] indicates the total ways to create the specified amount.

A Java solution might appear as follows: public int coinChange ( int [ ] coins , int amount ) { int [ ] dp = new int [ amount + 1 ] ; dp [ 0 ] = 1 ; for int coin : coins ) { for int x = coin ; x < amount + 1 ; ++ x ) { dp [ x ] += dp [ x - coin ] ; } } return dp [ amount ] ; } This Java function initializes an integer array called dp to keep track of the number of ways to form each amount leading up to the specified amount. It then iterates through each coin, updating the count of combinations for every amount that meets or exceeds the value of the current coin. This update involves adding the current count of combinations to the count for the amount that is decreased by the current coin's value. Ultimately, the function returns dp[amount], representing the total number of ways to achieve the desired amount.