Multiplication table

讓我們來懷舊一下，學校程式語言課程當中最常出現的考題，九九乘法表。

解題難度在於版面輸出，反而不是數學問題，幸好 Java 在 1.5 版後開始支援類似 C 的 printf() 方法，讓實作有了更大的彈性。

public static void main(String[] args) {
  java.io.PrintStream out = System.out;
  for (int i = 1; i <= 9; i += 3) {
     for (int j = 1; j <= 9; j++) {
        out.printf("%2d X %2d = %2d\t", i, j, i * j);
        out.printf("%2d X %2d = %2d\t", (i + 1), j, (i + 1) * j);
        out.printf("%2d X %2d = %2d\n", (i + 2), j, (i + 2) * j);
     }
     out.println();
  }
}

Source Code

 1 X  1 =  1  2 X  1 =  2  3 X  1 =  3
 1 X  2 =  2  2 X  2 =  4  3 X  2 =  6
 1 X  3 =  3  2 X  3 =  6  3 X  3 =  9
 1 X  4 =  4  2 X  4 =  8  3 X  4 = 12
 1 X  5 =  5  2 X  5 = 10  3 X  5 = 15
 1 X  6 =  6  2 X  6 = 12  3 X  6 = 18
 1 X  7 =  7  2 X  7 = 14  3 X  7 = 21
 1 X  8 =  8  2 X  8 = 16  3 X  8 = 24
 1 X  9 =  9  2 X  9 = 18  3 X  9 = 27

 4 X  1 =  4  5 X  1 =  5  6 X  1 =  6
 4 X  2 =  8  5 X  2 = 10  6 X  2 = 12
 4 X  3 = 12  5 X  3 = 15  6 X  3 = 18
 4 X  4 = 16  5 X  4 = 20  6 X  4 = 24
 4 X  5 = 20  5 X  5 = 25  6 X  5 = 30
 4 X  6 = 24  5 X  6 = 30  6 X  6 = 36
 4 X  7 = 28  5 X  7 = 35  6 X  7 = 42
 4 X  8 = 32  5 X  8 = 40  6 X  8 = 48
 4 X  9 = 36  5 X  9 = 45  6 X  9 = 54

 7 X  1 =  7  8 X  1 =  8  9 X  1 =  9
 7 X  2 = 14  8 X  2 = 16  9 X  2 = 18
 7 X  3 = 21  8 X  3 = 24  9 X  3 = 27
 7 X  4 = 28  8 X  4 = 32  9 X  4 = 36
 7 X  5 = 35  8 X  5 = 40  9 X  5 = 45
 7 X  6 = 42  8 X  6 = 48  9 X  6 = 54
 7 X  7 = 49  8 X  7 = 56  9 X  7 = 63
 7 X  8 = 56  8 X  8 = 64  9 X  8 = 72
 7 X  9 = 63  8 X  9 = 72  9 X  9 = 81

Program Output