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Commit 25e4fd70 authored by Goik Martin's avatar Goik Martin
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Loop Exercises

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......@@ -149,16 +149,154 @@
</qandaset>
</section>
<section xml:id="sd1SectIntermediateMultiplication">
<title>Intermediate Example, part 1: A multiplication table</title>
<qandaset defaultlabel="qanda"
xml:id="sd1QandaIntermediateMultiplyTable1">
<qandadiv>
<qandaentry>
<question>
<para>In order to prepare a more sophisticated square number
table we supply a slightly different exercise producing a
multiplication table:</para>
<programlisting language="none"> | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
---+----------------------------------------------------------------------------------------------------
1| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
2| 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
3| 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
4| 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80
5| 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
6| 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120
7| 7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140
8| 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160
9| 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144 153 162 171 180
10| 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
11| 11 22 33 44 55 66 77 88 99 110 121 132 143 154 165 176 187 198 209 220
12| 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240
13| 13 26 39 52 65 78 91 104 117 130 143 156 169 182 195 208 221 234 247 260
14| 14 28 42 56 70 84 98 112 126 140 154 168 182 196 210 224 238 252 266 280
15| 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300
16| 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256 272 288 304 320
17| 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255 272 289 306 323 340
18| 18 36 54 72 90 108 126 144 162 180 198 216 234 252 270 288 306 324 342 360
19| 19 38 57 76 95 114 133 152 171 190 209 228 247 266 285 304 323 342 361 380
20| 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400</programlisting>
<para>The number of rows and columns are equal. Provide an
appropriate parameter so that your implementation works for
different values just by changing tis single value.</para>
<tip>
<para>You'll need a loop nested within an outer one like:
</para>
<programlisting language="none">for (int y=0; &lt; limit; y++){
for (int x=0; x &lt; limit; x++) {
...
}
}</programlisting>
</tip>
</question>
<answer>
<programlisting language="none"> public static void main(String[] args) {
int limit = 10;
System.out.print(" | ");
for (int col = 1; col &lt;= limit; col++) { // Header line of columus from 1 to limit
System.out.format("%3d ", col);
}
System.out.println();
System.out.print("---+"); // Header / table body separator
for (int col = 1; col &lt;= limit; col++) {
System.out.print("-----");
}
System.out.println();
for (int row = 1; row &lt;= limit; row ++) { // Printing rows
System.out.format("%3d| ", row);
for (int col = 1; col &lt;= limit; col++) { // Printing columns
System.out.format("%3d ", row * col);
}
System.out.println();
}
}</programlisting>
</answer>
</qandaentry>
</qandadiv>
</qandaset>
</section>
<section xml:id="sd1SectIntermediateMultiplication2">
<title>Intermediate Example, part 2: Avoiding redundant entries</title>
<qandaset defaultlabel="qanda"
xml:id="sd1QandaIntermediateMultiplyTable2">
<qandadiv>
<qandaentry>
<question>
<para>It does not make sense to supply both results like e.g. 3
* 4 and 4 * 3. Modify your application to generate:</para>
<programlisting language="none"> | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
---+----------------------------------------------------------------------------------------------------
1| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
2| 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
3| 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60
4| 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80
5| 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
6| 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120
7| 49 56 63 70 77 84 91 98 105 112 119 126 133 140
8| 64 72 80 88 96 104 112 120 128 136 144 152 160
9| 81 90 99 108 117 126 135 144 153 162 171 180
10| 100 110 120 130 140 150 160 170 180 190 200
11| 121 132 143 154 165 176 187 198 209 220
12| 144 156 168 180 192 204 216 228 240
13| 169 182 195 208 221 234 247 260
14| 196 210 224 238 252 266 280
15| 225 240 255 270 285 300
16| 256 272 288 304 320
17| 289 306 323 340
18| 324 342 360
19| 361 380
20| 400</programlisting>
</question>
<answer>
<para>The required change with respect to the previous exercise
is actually very small. We need <code>col = row</code> rather
than <code>col = 1</code>:</para>
<programlisting language="none"> for (int row = 1; row &lt;= limit; row ++) { // Printing rows
System.out.format("%3d| ", row);
for (int <emphasis role="bold">col = row;</emphasis> col &lt;= limit; col++) { // Printing columns
System.out.format("%3d ", row * col);
}
System.out.println();
}</programlisting>
</answer>
</qandaentry>
</qandadiv>
</qandaset>
</section>
<section xml:id="sd1SectSquareTableBlocks">
<title>Creating a <quote>real</quote> table</title>
<title>Creating a <quote>real</quote> square table</title>
<qandaset defaultlabel="qanda" xml:id="sd1QandaSquareTableBlocks">
<qandadiv>
<qandaentry>
<question>
<para>The last solution is only appropriate for smaller amounts
of data. Letting the number of elements grow requires
rearranging values in blocks:</para>
<para>The last square number table solution is only appropriate
for smaller amounts of data. Letting the number of elements grow
requires rearranging values in blocks:</para>
<programlisting language="none"> n | n*n n | n*n n | n*n n | n*n n | n*n
----+--------------+--------------+--------------+--------------+----------
......@@ -184,8 +322,7 @@
18 | 324 38 | 1444 58 | 3364 78 | 6084 98 | 9604
19 | 361 39 | 1521 59 | 3481 79 | 6241 99 | 9801</programlisting>
<para>Building a table this way will require some
parameters:</para>
<para>Building a table this way requires some parameters:</para>
<itemizedlist>
<listitem>
......@@ -204,7 +341,7 @@
</listitem>
</itemizedlist>
<para>You may have to nest loops within each other.</para>
<para>You may have to nest three loops within each other.</para>
</question>
<answer>
......
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