7. Algorithm design and problem-solving
A section of Computer Science, 2210
Listing 10 of 38 questions
This pseudocode algorithm is intended to allow, at random, between 1 and 20 values to be entered and totalled. The total and average of the entered values are output at the end of the algorithm. 01 DECLARE Loop : STRING 02 DECLARE Limit : INTEGER 03 DECLARE Value : REAL 04 DECLARE Total : REAL 05 Total 06 Limit ROUND(RANDOM() * 19,0) + 1 07 IF Loop 1 TO Limit 08 OUTPUT "Enter a number" 09 INPUT Loop 10 Total Total * Value 11 NEXT Loop 12 OUTPUT "The total of the numbers entered is ", Total 13 OUTPUT "The average of the numbers entered is ", Total / Limit Identify the line numbers of four errors in the pseudocode and suggest corrections. Error 1 line number Correction Error 2 line number Correction Error 3 line number Correction Error 4 line number Correction Write the pseudocode statement that would output the average calculated in line 13 of the algorithm rounded to one decimal place. Explain how you should alter the original corrected algorithm to make sure that all the numbers entered are between 1 and 500 inclusive. If any numbers fall outside these limits, a replacement value is requested and entered. You do not need to re-write the algorithm.
2210_s24_qp_21
THEORY
2024
Paper 2, Variant 1
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The flowchart represents an algorithm. INPUT Limit Count 1 No START STOP OUTPUT Numbers INPUT Numbers Result Limit DIV 2 + 1 Swap Numbers Numbers Numbers[Count + 1] Numbers[Count + 1] Swap Flag True Count Count + 1 IS Count > Limit? Count Count + 1 Flag TRUE Yes No No No Yes Yes Yes Flag False Count 1 IS Numbers > Numbers[Count + 1]? IS Count > Limit – 1? IS Flag = TRUE? Complete the trace table for the input data: 7, 47, 50, 52, 60, 80, 63, 70 Numbers Limit Count Flag Swap Result OUTPUT Outline the processes involved in the algorithm shown in the flowchart on page 6.
2210_s24_qp_21
THEORY
2024
Paper 2, Variant 1
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An algorithm has been written in pseudocode to allow the names of 50 cities and their countries to be entered and stored in a two‑dimensional (2D) array. The contents of the array are then output. 01 DECLARE City ARRAY[1:50, 1:2] OF BOOLEAN 02 DECLARE Count : INTEGER 03 DECLARE Out : INTEGER 04 Count 05 IF 06 OUTPUT "Enter the name of the city" 07 INPUT City[Count, 2] 08 OUTPUT "Enter the name of the country" 09 INPUT City[Count, 2] 10 Count Count + 1 11 UNTIL Count = 50 12 FOR Out 1 TO 1 13 OUTPUT "The city ", City[Out, 1], " is in ", City[Out, 2] 14 NEXT Out Identify the four errors in the pseudocode and suggest corrections. Error 1 Correction Error 2 Correction Error 3 Correction Error 4 Correction Describe the changes you should make to the corrected algorithm to allow the name of a country to be input and to display only the stored cities from that country. You do not need to rewrite the algorithm.
2210_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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The flowchart represents an algorithm that performs a process on groups of values that are input. The algorithm will fail if the first value of any group is 0. An input of –1 will terminate the algorithm. START STOP Total 0 Count 0 INPUT Value IS Value = 0 ? IS Value = –1 ? No No Yes Yes Total Total + Value Count Count + 1 Average Total / Count OUTPUT "Total is ", Total OUTPUT "Average is ", Average Complete the trace table for the input data: 25, 35, 3, 0, 57, 20, 25, 18, 0, –1, 307, 40, 0 Value Average Total Count OUTPUT Describe the purpose of the algorithm.
2210_w23_qp_22
THEORY
2023
Paper 2, Variant 2
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Four flowchart symbols and five purposes are shown. Draw one line to link each flowchart symbol to its correct purpose. Not all purposes will be used. Flowchart symbol Purpose subroutine process flow decision terminator An algorithm needs to total 50 numbers between 1 and 100 inclusive. Draw a flowchart that: • uses a count-controlled loop from 1 to 50 • uses an appropriate prompt to ask for a number between 1 and 100 • totals the numbers as they are entered • outputs the total after the loop has completed with an appropriate message.
2210_w24_qp_22
THEORY
2024
Paper 2, Variant 2
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This pseudocode represents an algorithm. An input of –1 will terminate the algorithm. DECLARE Count : INTEGER DECLARE Answer : INTEGER DECLARE Value : INTEGER REPEAT INPUT Value IF Value <> -1 THEN Answer Value FOR Count Value - 1 TO 1 STEP -1 Answer Answer * Count NEXT Count OUTPUT Answer ENDIF UNTIL Value = -1 Complete the trace table for the input data: 5, 6, –1, 20, 9, 4 Value Count Answer OUTPUT State the purpose of this algorithm. Describe the problem that would be caused in this algorithm if a Value of 1, 0 or less than –1 was input.
2210_w24_qp_22
THEORY
2024
Paper 2, Variant 2
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Questions Discovered
38