// APS101, Winter 2009: Lecture 22 (Mar. 5)
//
// Assignment 2 note: to get full marks for PassportTester.java and SpyTester.java
                      you must test all the methods THOROUGHLY. (i.e. sometimes you 
                      should test the method with several different inputs, if it's a 
                      more complex method, like addVisited in Passport).
//
// Review: last time we wrote two new versions of the isPalindrome method, to
// improve efficiency. 
// we also looked at method "mystery" in WhileDemo and practiced tracing the code.
// what was difficult about this method? 2 while loops that were NESTED! (one inside the other)

// to get some more practice with nested loops, we wrote the method
// sentenceWordSplit in NestedLoops.java (take a look at it).

// questions regarding tracing code, especially with nested loops, will definitely be on
// your final exam, so get as much practice with them as possible. 

// (see method example1() in ForDemo)

// (see method example2() in ForDemo)

// A2 clarification: method "stretch" in the Spy class
//
// let's say we have a key = "1101"
// (which is the binary representation of integer 13,
    but it doesn't matter how we got the key)

// then we want to stretch it...
//
// stretch(key, 2) -> "1101"   // there is no change
// stretch(key, 4) -> "1101"   // also no change, because key is already 4 bits long
// stretch(key, 5) // the following happens, according to the algorithm:
// half 1 = "11"
// half 2 = "01"  // XOR the bits
// result = "10"  // then append the result to the end of the current key
// key = key + "10"
// key = "110110"
// so stretch(key, 5) -> "110110"

// how about stretch(key, 8)? repeat the process once more:
// half 1 = "110"
// half 2 = "110"
// result = "000"
// key = key + "000"
// key = "110110000
// so stretch(key, 8) -> "110110000"