7 problem solving with loops
- 1. Data Structures and Algorithms Problem Solving with Loops The Loop Logic Structure A third logic structure for designing decisions is the loop structure. The loop logic structure is the repeating structure. Types of Loop Structures @ WHILE / WHILE-END @ REPEAT / UNTIL @ AUTOMATIC COUNTER LOOP Incrementing The task of incrementing, or counting, is done by adding a constant, such as 1 or 2, to the value of a variable. To write the instruction to increment a variable, you use an assignment statement. For example: COUNTER = COUNTER + 1 or C = C+ 1 Problem Solving with Loops *Property of STI Page 1 of 18
- 2. Data Structures and Algorithms Problem Solving with Loops Accumulating Another task that a program must often perform is accumulating, or summing a group of numbers. The process of accumulating is similar to incrementing, except a variable instead of a constant is added to another variable, which holds the value of the sum or total. The instruction for accumulating is the following : SUM = SUM + VARIABLE PRODUCT = PRODUCT * NUMBER Problem Solving with Loops *Property of STI Page 2 of 18
- 3. Data Structures and Algorithms Problem Solving with Loops WHILE / WHILE - END The first of the three types of loop structures is the WHILE/WHILE-END structure. This type of loop tells the computer that while the condition is TRUE, repeat all instructions between the WHILE and the WHILE- END. The form of the algorithm is the following: WHILE <CONDITION(S)> INSTRUCTION INSTRUCTION . . . WHILE-END Problem Solving with Loops *Property of STI Page 3 of 18
- 4. Data Structures and Algorithms Problem Solving with Loops Flowchart Diagram of WHILE/WHILE-END Problem Solving with Loops *Property of STI Page 4 of 18
- 5. Data Structures and Algorithms Problem Solving with Loops Decision Equivalent to WHILE/WHILE-END Problem Solving with Loops *Property of STI Page 5 of 18
- 6. Data Structures and Algorithms Problem Solving with Loops Problem : Create the algorithm and the flowchart to find the average age of all the students in a class. Problem Solving with Loops *Property of STI Page 6 of 18
- 7. Data Structures and Algorithms Problem Solving with Loops Repeat/Until The second type of loop structure is the REPEAT/UNTIL structure. This type of loop tells the computer to repeat the set of instructions between the REPEAT and the until, until a condition is TRUE. The format of the REPEAT/UNTIL algorithm is the following: Repeat Instruction Instruction . . . Until <condition(s)> Problem Solving with Loops *Property of STI Page 7 of 18
- 8. Data Structures and Algorithms Problem Solving with Loops Flowchart Diagram of REPEAT/UNTIL Problem Solving with Loops *Property of STI Page 8 of 18
- 9. Data Structures and Algorithms Problem Solving with Loops Decision Equivalent to REPEAT/UNTIL Problem Solving with Loops *Property of STI Page 9 of 18
- 10. Data Structures and Algorithms Problem Solving with Loops Problem : Create the algorithm and the flowchart to find the average age of all the students in a class. Problem Solving with Loops *Property of STI Page 10 of 18
- 11. Data Structures and Algorithms Problem Solving with Loops Automatic – Counter Loop The third type of loop structure is the automatic- counter loop. This type of loop increments or decrements a variable each time the loop is repeated. The form of the algorithm for the automatic counter- loop is the following : LOOP:COUNTER = BEGIN TO END STEP S INSTRUCTION INSTRUCTION . . . LOOP-END: COUNTER Problem Solving with Loops *Property of STI Page 11 of 18
- 12. Data Structures and Algorithms Problem Solving with Loops Decision Equivalent to Automatic-Counter Loop Problem Solving with Loops *Property of STI Page 12 of 18
- 13. Data Structures and Algorithms Problem Solving with Loops Problem : Create the algorithm and the flowchart to find the average age of all the students in a class. Problem Solving with Loops *Property of STI Page 13 of 18
- 14. Data Structures and Algorithms Problem Solving with Loops Nested Loops Loops can be nested like decisions can. Each loop must be nested inside the loop just outside it. The general rules regarding loops, such as where the condition is processed and how indentation and brackets are used, hold true for nested loops as well as single loops. The inner loops do not have to be the same types of loop structures as the outer loops; that is, a WHILE/ WHILE-END may be nested inside a REPEAT/UNTIL loop, or vice versa. Problem Solving with Loops *Property of STI Page 14 of 18
- 15. Data Structures and Algorithms Problem Solving with Loops Nested Loops Problem Solving with Loops *Property of STI Page 15 of 18
- 16. Data Structures and Algorithms Problem Solving with Loops Problem Solving with Loops *Property of STI Page 16 of 18
- 17. Data Structures and Algorithms Problem Solving with Loops Indicators Indicators – are logical variables that a programmer sets within a program to change the processing path or to control when the processing of a loop should end. They are sometimes called flags, switches, or trip values. Recursion Another type of loop structure is recursion. Recursion occurs when a module or a function calls itself. Problem Solving with Loops *Property of STI Page 17 of 18
- 18. Data Structures and Algorithms Problem Solving with Loops Problem Solving with Loops *Property of STI Page 18 of 18