tugas alpro -2

FUNDAMENTAL ALGORITHMS EXCHANGING THE VALUES OF TWO VARIABLES problem given two variables, a and b, exchange the values assigned to them. the problem of interchanging the values associated with two variables involves a very fundamental menchanism that occurs in many sorting and data manipulation algorithms. To define the problem more clearly we will examine a specific example. Algorithm Development The problem of interchanging the values associated two variables involves a very fundamental mechanism that occurs in many sorting and data manipulation algorithms. Algorithms Description 1. Save the original value of a in t. 2. Assign to a the original value of b. 3. Assign to b the original value of a that is stored in t. Pascal Implementation Procedure exchange (var a,b : integer); Var t : integer; begin {save the original value of a then exchange a and b} {assert : a=a0^b=b0} t:=a; a:=b; b:=t; {assert : a=a0^b=a0} end Notes of Design 1. The use of an intermediate temorary variable allows the exchange of two variables to proceed correctly. 2. This example emphasizes that at any stage in a computation a variable always assumes the value dictated by the most recent assigment made to that variable. 3. Working through the mechanism with a particular example can be a useful way of detecting design faults. 4. A more common application of exchange involves two array elements. Applications Sorting algoritms.