corejava第10版

corejava第10版/v1ch03/LotteryArray/LotteryArray.java

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+/**
+ * This program demonstrates a triangular array.
+ * @version 1.20 2004-02-10
+ * @author Cay Horstmann
+ */
+public class LotteryArray
+{
+   public static void main(String[] args)
+   {
+      final int NMAX = 10;
+
+      // allocate triangular array
+      int[][] odds = new int[NMAX + 1][];
+      for (int n = 0; n <= NMAX; n++)
+         odds[n] = new int[n + 1];
+
+      // fill triangular array
+      for (int n = 0; n < odds.length; n++)
+         for (int k = 0; k < odds[n].length; k++)
+         {
+            /*
+             * compute binomial coefficient n*(n-1)*(n-2)*...*(n-k+1)/(1*2*3*...*k)
+             */
+            int lotteryOdds = 1;
+            for (int i = 1; i <= k; i++)
+               lotteryOdds = lotteryOdds * (n - i + 1) / i;
+
+            odds[n][k] = lotteryOdds;
+         }
+
+      // print triangular array
+      for (int[] row : odds)
+      {
+         for (int odd : row)
+            System.out.printf("%4d", odd);
+         System.out.println();
+      }
+   }
+}