CSC530 Data Structure - Decision Zhen Jiang Dept. of Computer Science West Chester University West Chester, PA 19383 zjiang@wcupa.edu

Selection (Decision) Introduction T/F selection MC selection

Selection (Decision) Rolling a dice. Sample execution (click on this link to try) Each button in the above sample has

No Yes Win/Lost? Double the money Bankrupt Restart

If else statement if (test) action 1 (statements 1) else action 2 (statements 2) //end if action 3 (statement 3)

No Yes Test by boolean expression Action 1 Action 2 Action 3

Boolean expression in test Simple expression Format <Value> <relational operators> <Value> Number value relational operators ==, !=, <, >, <=, >= !!! Number one error: “(a=2)” instead of “(a==2)” char value (not string!) relational operators ==, !=

Complex expression &&, ||, ! Truth table Precedence order Number range

Development of a correct decision program Grade.java

Development Process Identify two exclusive options Implement each handling in different action parts Identify the situation (values) for option selection Make an expression so that all the situation value for option part 1 will lead to the test result (boolean value) true. Verify all the situation value for option part 2 will lead to the test false, otherwise, revise the above expression!

If statement Relational operator ? Multiple selection Nested if If else if Example: letter grade

Comments: Nested if for multiple selection problem If case 1 else if … //end of case 2 if //End of case 1 if

Development of a correct multiple-decision program Letter grade

Switch Switch([variable]) Case [constant value]: Break (or no break)