Algorithm for Decision Structures & Looping Structures
Decision Structures : Two - Way SelectionIf - Else :
if condition True alternative else False alternative end if
Example :
if A > B then Write ( A ) else Write ( B ) end if
Nested - If :
if condition True alternative else False alternative end if else False alternative end if
Example : Finding the maximum of three numbers using Nested - If
Read (A, B, C) If A > B then if A > C then max <- A else max <- C end if else if B > C then max <- B else max <- C end if end if Write("Largest value is ", max) Halt
Decision Structure : Multi - Way Selection
Switch - Case : select (expression) from { case val1 : statements; break; case val2 : statements; break; -------- -------- default; }
Looping Structure : repeat....while
repeat through step Sn while condition.
-The steps specified in the repeat through statement is the range of loop.
-Sn - steps from repeat statement up to and including step Sn.
Example : Read numbers fro keyboard & print total.
- Start
- Sum <- 0
- Read (num)
- repeat thru step 6 while num > 0
- Sum <- Sum + num
- Read (num)
- Write (Sum)
- Stop
Looping Structure : for
- used if number of repetitions are known before.
- repeat range of loop for values of loop_control_variable.
Example :
- Repeat through step n for i <- 1 to 10
- Repeat for val <- 1 to N
------------
------------
End repeat - Repeat thru step 10 for index -9 to -3 by 3
- Repeat for count <- 2 to 18 by 2
Example : Factorial of a Given Number
- Start
- Read ( N )
- Fact <- 1
- Repeat for i <- N to 1 by -1
fact <- fact * 1
End repeat - Write ("factorial of N is ", fact)
- Stop
Looping Structure : Do - While
Used when the loop need to be executed at least once.
the loop repeat until the condition is satisfied.
Repeat for i <- 1 to N ------ ------ if condition then end repeat until condition Exit loop End if ------ ------ End repeat
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