Added some tests and benchmarks

Author: jeandersonbc

training/RecursiveCoinChange.java

@@ -1,8 +1,16 @@
 import java.util.Arrays;
 
+/*
+ * Given an arbitrary amount of money and a set of coin denominations,
+ * do you know how to compute the minimum number of coins necessary
+ * to change the informed amount of money?
+ *
+ * For instance, given $25 and the coins $1, $5, and $10, you can change
+ * $25 with at least 3 coins: 10+10+5
+ */
 class Main {
 
- /* This recursive approach solves the problem corretly
+ /* This recursive approach solves the problem correctly
  * but it does not scale for large inputs.
  *
  * Can you guess why? :)
@@ -41,23 +49,44 @@ static int faster(int value, int[] coins) {
  return minCoins[value];
  }
 
+ static void correctness(int testValue, int[] testCoins) {
+ System.out.printf("Test Value: %d, Test Coins: %s\n", testValue, Arrays.toString(testCoins));
+ int sol1 = solve(testValue, testCoins);
+ int sol2 = faster(testValue, testCoins);
+ if (sol1 != sol2) {
+ System.err.printf("Wrong Answer - Recursive: %d, DP: %d\n", sol1, sol2);
+ } else {
+ System.out.printf("Correct Answer: %d\n", sol2);
+ }
+ }
+
+ static void efficiency(int minValue, int maxValue, int[] testCoins) {
+ System.out.println("N\tNaive\tDP");
+ for (int testValue = minValue; testValue <= maxValue; testValue += 10) {
+ long t1 = System.currentTimeMillis();
+ solve(testValue, testCoins);
+ t1 = System.currentTimeMillis() - t1;
+
+ long t2 = System.currentTimeMillis();
+ faster(testValue, testCoins);
+ t2 = System.currentTimeMillis() - t2;
+
+ System.out.printf("%d\t%d\t%d\n", testValue, t1, t2);
+ }
+ }
+
+ // Some tests...
  public static void main(String[] args) {
- int value = 25;
- int[] coins = {5, 10, 15};
- System.out.println(value + " " + Arrays.toString(coins));
- System.out.println(solve(value, coins));
- System.out.println(faster(value, coins));
-
- value = 40;
- coins = new int[]{5, 10, 25, 50};
- System.out.println(value + " " + Arrays.toString(coins));
- System.out.println(solve(value, coins));
- System.out.println(faster(value, coins));
-
- value = 40;
- coins = new int[]{5, 10, 20, 25, 50};
- System.out.println(value + " " + Arrays.toString(coins));
- System.out.println(solve(value, coins));
- System.out.println(faster(value, coins));
+ correctness(25, new int[]{5, 10, 15});
+ correctness(40, new int[]{5, 10, 25, 50});
+ correctness(40, new int[]{5, 10, 20, 25, 50});
+ correctness(7, new int[]{1, 3, 4, 5});
+
+ System.out.println("----------");
+ efficiency(100, 150, new int[]{5, 10, 20, 25, 50});
+
+ System.out.println("----------");
+ int sol = faster(10_000_000, new int[]{5, 10, 20, 25, 50});
+ System.out.printf("For N = 10^7, Coin Change = %d\n", sol);
  }
 }