#322 换硬币 dp

Author: Isaaclot

main/src/dynamic_programming/LC_322_CoinChange.java

@@ -0,0 +1,28 @@
+package dynamic_programming;
+
+import java.util.Arrays;
+
+/**
+ * @author liangqian0723@gmail.com
+ * @since 2020/3/8 8:43 AM
+ */
+public class LC_322_CoinChange {
+    /**
+     * 重复子问题：
+     * dp存储空间
+     * dp方程:
+     */
+    public int coinChange(int[] coins, int amount) {
+        int[] dp = new int[amount + 1];
+        int max = amount + 1;
+        Arrays.fill(dp, max);
+        dp[0] = 0;
+        for (int i = 1; i <= amount; ++i) {
+            for (int coin : coins) {
+                if (i < coin) continue;
+                dp[i] = Math.min(dp[i], 1 + dp[i - coin]);
+            }
+        }
+        return (dp[amount] == amount + 1) ? -1 : dp[amount];
+    }
+}

main/test/dynamic_programming/LC_322_CoinChangeTest.java

@@ -0,0 +1,18 @@
+package dynamic_programming;
+
+import org.junit.Test;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * @author liangqian0723@gmail.com
+ * @since 2020/3/8 8:41 AM
+ */
+public class LC_322_CoinChangeTest {
+    @Test
+    public void change_coin_by_min_num_test(){
+        LC_322_CoinChange cc  = new LC_322_CoinChange();
+        assertThat(cc.coinChange(new int[]{186,419,83,408}, 6249), is(20));
+    }
+}