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Tracing array totals through iteration
Figure 6 shows an algorithm, represented using pseudo-code.
| days ← [10, 15, 4] |
| sales ← [20, 33, 12] |
| weeks ← [0, 0, 0] |
| FOR i ← 0 TO 2 |
| daysTotal ← days[i] + sales[i] |
| weeks[i] ← daysTotal DIV 7 |
| ENDFOR |
| weeksTotal ← weeks[0] + weeks[1] + weeks[2] |
| OUTPUT weeksTotal |
The DIV operator is used for integer division.
Complete the trace table for the algorithm in Figure 6. Part of the table has already been filled in. You may not need to use all the rows in the table.
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Marking points
- 1 Traces i as 0, 1, 2.
- 2 Calculates the first daysTotal as 30.
- 3 Calculates the later daysTotal values as 48 and 16.
- 4 Updates weeks[0] to 4.
- 5 Retains and updates the entire weeks array through all three iterations.
- 6 Places only the final total 12 in weeksTotal, subject to official follow-through guidance.
Why this answer loses marks
On each iteration I reset the array and wrote only the newest changed element.
The trace must retain earlier array updates, or the final state and total will no longer follow the algorithm.