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| 1 | +using System; |
| 2 | +using System.Linq; |
| 3 | + |
| 4 | +public class Solution |
| 5 | +{ |
| 6 | + private static int[] _InitializeDP(int amount) |
| 7 | + { |
| 8 | + // Set an impossible value for all amounts to indicate they haven't been solved yet |
| 9 | + int[] dp = Enumerable.Repeat(amount + 1, amount + 1).ToArray(); |
| 10 | + |
| 11 | + dp[0] = 0; // No coins are needed to make 0 |
| 12 | + return dp; |
| 13 | + } |
| 14 | + |
| 15 | + private static void _CalculateMinCoins(int[] coins, int[] dp) |
| 16 | + { |
| 17 | + for (int i = 1; i < dp.Length; i++) |
| 18 | + { |
| 19 | + foreach (int coin in coins) |
| 20 | + { |
| 21 | + if (i >= coin) // equals to (i - coin >= 0) |
| 22 | + { |
| 23 | + dp[i] = Math.Min(dp[i], 1 + dp[i - coin]); |
| 24 | + } |
| 25 | + } |
| 26 | + } |
| 27 | + } |
| 28 | + |
| 29 | + private static int _GetCoinChangeResult(int[] dp, int amount) |
| 30 | + { |
| 31 | + return (dp[amount] > amount) ? -1 : dp[amount]; |
| 32 | + } |
| 33 | + |
| 34 | + public static int CoinChange(int[] coins, int amount) |
| 35 | + { |
| 36 | + if (coins == null || coins.Length == 0) |
| 37 | + { |
| 38 | + return -1; |
| 39 | + } |
| 40 | + |
| 41 | + if (amount == 0) |
| 42 | + { |
| 43 | + return 0; |
| 44 | + } |
| 45 | + |
| 46 | + int[] dp = _InitializeDP(amount); |
| 47 | + _CalculateMinCoins(coins, dp); // Calculate the minimum coins for each amount |
| 48 | + return _GetCoinChangeResult(dp, amount); |
| 49 | + } |
| 50 | + |
| 51 | + public static void Main(string[] args) |
| 52 | + { |
| 53 | + int[] coins = { 1, 6, 7, 9, 11 }; |
| 54 | + |
| 55 | + Console.WriteLine(CoinChange(coins, 13)); |
| 56 | + |
| 57 | + Console.ReadKey(); |
| 58 | + } |
| 59 | +} |
| 60 | + |
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