feat: solved 322

Author: fghpdf

src/com/fghpdf/CoinChange/Solution.java

@@ -0,0 +1,50 @@
+package com.fghpdf.CoinChange;
+
+/**
+ * @author fghpdf
+ * @date 2019/12/29
+ * https://leetcode.com/problems/coin-change/
+ * dp coins [1,2,5] amount 11
+ * dp[0] is 0
+ * dp[1] is 1. coin 1
+ * dp[2] is 1. coin 2. min(coin 2 + dp[0]...coin 1 + dp[1])
+ * ...
+ * dp[11] is 3. min(coin 5 + dp[6]...coin 3 + dp[8]...coin 1 + dp[10])
+ **/
+public class Solution {
+	public int coinChange(int[] coins, int amount) {
+		if (amount < 1) {
+			return amount;
+		}
+		return helper(coins, amount, new int[amount]);
+	}
+
+	private int helper(int[] coins, int rem, int[] dp) {
+		if (rem < 0) {
+			return -1;
+		}
+
+		if (rem == 0) {
+			return 0;
+		}
+
+		if (dp[rem - 1] != 0) {
+			return dp[rem - 1];
+		}
+
+		int min = Integer.MAX_VALUE;
+		for (int coin : coins) {
+			int res = helper(coins, rem - coin, dp);
+			if (res >= 0 && res < min) {
+				min = res + 1;
+			}
+		}
+		dp[rem - 1] = (min == Integer.MAX_VALUE) ? -1 : min;
+		return dp[rem - 1];
+	}
+
+	public static void main(String[] args) {
+		Solution solution = new Solution();
+		System.out.println(solution.coinChange(new int[]{1, 2, 5}, 11));
+	}
+}